Slide 1

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone
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





The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF
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

When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems
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




The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations
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





The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs
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




In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth
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




A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth
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




Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)
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



If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless
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



Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control
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



Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)
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



All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs
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


Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)
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


An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)
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



The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System
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



The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System
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





Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)
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




The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)
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




No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 2

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 3

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 4

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 5

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 6

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 7

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 8

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 9

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 10

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 11

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 12

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 13

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 14

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 15

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 16

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 17

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 18

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 19

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 20

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 21

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 22

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 23

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 24

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 25

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 26

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 27

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 28

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 29

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 30

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 31

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 32

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 33

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 34

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 35

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 36

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 37

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 38

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 39

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 40

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 41

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 42

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 43

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 44

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 45

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 46

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 47

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 48

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 49

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 50

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 51

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 52

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 53

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 54

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 55

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 56

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 57

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 58

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 59

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.


Slide 60

Principles of Electronic
Communication Systems
Second Edition
Louis Frenzel

© 2002 The McGraw-Hill Companies

Principles of Electronic
Communication Systems
Second Edition
Chapter 20

Wireless Technologies

©2003 The McGraw-Hill Companies

Wireless Technologies







Wireless refers primarily to the cellular telephone industry.
Wireless is also used to refer to some other radiolike services,
including wireless local-area networks (LANs) and personalarea networks (PANs).
Other special wireless systems are radio frequency
identification (RFID) systems and numerous infrared wireless
devices.
Ultrawideband (UWB) is a technology used in wireless
networking and low-cost short-range radar systems.

Topics Covered in Chapter 20








Cellular Telephone Systems
Digital Cell Phone Systems
Wireless LANs and PANs
PANs and Bluetooth
Infrared Wireless
Radio Frequency Identification
Ultrawideband Wireless

Cellular Telephone Systems





A cellular radio system provides standard telephone
service by two-way radio at remote locations.
Cellular radios or telephones were originally installed
in cars or trucks, but today most of them are available
in handheld models.
Cellular telephones permit users to link up with the
standard telephone system, which permits calls to any
part of the world.

Cellular Telephone Systems
(Continued)





Cellular radio telephone service is available
nationwide.
The original cell phone system, known as the
advanced mobile phone system, or AMPS, was based
on analog technologies.
Although AMPS is still in use, it has gradually been
phased out by second- (2G) and third-generation (3G)
digital cell phone systems.

Cellular Concepts





The basic concept behind the cellular radio system is
that rather than serving a given geographical area
with a single transmitter and receiver, the system
divides the service area into many small areas known
as cells.
The typical cell covers only several square miles and
contains its own receiver and low-power transmitter.
The coverage of a cell depends upon the density
(number) of users in a given area.

Cellular Concepts (Continued)






Each cell is connected by telephone lines or a
microwave radio relay link to a master control center
known as the mobile telephone switching office
(MTSO).
The MTSO controls all the cells and provides the
interface between each cell and the main telephone
office.
As the vehicle containing the telephone passes
through a cell, it is served by the cell transceiver.

Cellular Concepts (Continued)





The telephone call is routed through the MTSO and
to the standard telephone system.
As the vehicle moves, the system automatically
switches from one cell to the next.
The cellular system operates primarily in the 800- to
900-MHz range.
A newer cellular band, designated the personal
communications system (PCS) band extends from
1850 to 1990 MHz and is called PCS-1900.

Cellular Telephone Coverage Cells

AMPS Handset








Although AMPS cell phones are gradually being
phased out, millions are still in use.
An AMPS unit consists of five major sections:
transmitter, receiver, synthesizer, logic unit, and
control unit.
Mobile radios derive their operating power from the
car battery.
Portable units contain built-in rechargeable batteries.
The transmitter and receiver share a single antenna.

AMPS Unit Block Diagram

Digital Cell Phone Systems





Most new cell phones and systems use digital rather
than analog methods.
All-digital systems were developed primarily to
expand the capacity of existing cell phone systems.
Digital techniques provide several ways to multiplex
many users into the same spectrum space.
Digital systems are more reliable in a noisy
environment.

Digital Cell Phone Systems
(Continued)






Digital circuits can be made smaller and more powerefficient and therefore handsets can be more compact
and can operate for longer periods of time on a single
battery charge.
Digital cell phones greatly facilitate the transmission
of data as well as voice so that data services like
email and Internet access are possible with a cell
phone.
Most modern digital phones are referred to as secondand third-generation (2G and 3G) phones.

2G Cell Phone Systems






Three basic second-generation (2G) digital cell phone
systems are in wide use today.
Two of them use time division multiplexing (TDM),
and the third uses spread spectrum (SS).
The TDM systems are the Global System for Mobile
Communications (GSM) and the IS-136 standard for
time division multiple access (TDMA).
The SS system is code division multiple access
(CDMA).

Vocoder






To use digital data transmission techniques first
requires that the voice be digitized.
The circuit that does this is a vocoder, a special type
of analog-to-digital (A/D) converter and digital-toanalog (D/A) converter.
With voice frequencies as high as 4 kHz, the
minimum Nyquist sampling rate is 8 kHz.
The A/D in a vocoder should sample the voice signal
every 125 μs and generate a proportional binary
word.

Vocoder (Continued)







This serial data signal, representing the voice, is now
used to modulate the carrier and the composite signal
transmitted over the assigned channel.
The other technique is data compression.
Data compression techniques process the digitized
voice signal in such a way as to reduce the number of
bits needed to represent the voice reliably.
In modern cell phones a variety of vocoding data
compression schemes are used.

IS-136 TDMA






IS-136 (IS means interim standard) is the
Telecommunications Industry Association (TIA)
standard that fully describes the time division
multiple access (TDMA) cell phone system.
TDMA is also known as digital AMPS (DAMPS),
American digital cellular (ADC), or North American
TDMA (NA-TDMA).
IS-136 operates concurrently on the same 800- to
900-MHz band channels used by AMPS and is also
used in the PCS-1900 bands.

Global System for Mobile
Communications






The most widely used 2G digital system is GSM.
GSM originally stood for Group Special Mobile but
has become known as Global System for Mobile
Communications.
GSM is widely implemented in both the 800- and
1900-MHz personal communication system band.
It is gradually replacing the IS-136 systems in the
United States.

IS-95 CDMA







The IS-95 CDMA TIA cell phone standard is called
code division multiple access (CDMA) and is also
known as CDMA One.
CDMA uses direct sequence spread spectrum (DSSS)
with a 1.2288-MHz chipping rate that spreads the
signal over a 1.25-MHz channel.
Up to 64 users can use this band simultaneously with
little or no interference or degradation of service.
The CDMA system uses FDD for duplexing.

Digital Cell Phone Circuits





Digital cell phones are quite different from analog
phones.
Because they use digital techniques and pulse
modulation methods, and since massive growth in
cellular usage has caused spectrum crowding and
interference problems, new architectures and circuits
have been developed.
A variety of different circuits have been created to
accommodate numerous standards.

Digital Cell Phone Circuits
(Continued)





Three major trends dominate the cell phone
evolution: increased digital processing, increased
integration of circuitry on a few chips, and
multimode/multiband phones.
Most new digital phones also contain AMPS circuitry.
If a subscriber roams into an area lacking a carrier
that uses digital technology, the phone reverts to
analog, which is still supported in most areas.

2G Digital Cell Phone








The RF section contains the transmitter and receiver circuits
including mixers, local oscillators or frequency synthesizers
for channel selection, the receiver LNA, and the transmitter
power amplifier.
The baseband section contains the vocoder with it’s a/D and
D/A converters plus a DSP chip that handles many processing
functions.
An embedded controller handles all the digital control and
signaling, handoffs, and connection and identification
operations.
The controller also runs the display and keyboard and all other
user functions such as number storage, auto dialing, and caller
ID.

Direct Conversion






Superheterodyne designs are still used, however,
variations such as direct-conversion and very low IF
designs have been implemented.
The direct-conversion or zero IF design sets the LO
frequency to the incoming signal frequency so that
the translation is directly to the baseband signal.
Since direct conversion works only with doublesideband suppressed (DSB) AM signals, changes
have been made to accommodate FSK, BPSK, QPSK,
and other forms of digital modulation.

Direct Conversion (Continued)





Direct conversion eliminates the need for an
expensive and physically large selective IF filter.
Direct conversion eliminates the imaging problem so
common in superheterodyne designs, especially in the
crowded multiband cellular spectrum.
With direct conversion, baseband filtering can be
accomplished using simple low-pass RC filters and/or
DSP filters.

Direct Conversion Receiver

Low IF






When an IF is used near the baseband frequencies,
filtering is simple and very effective.
Most 2G and later phones are multiband phones that
can operate in two or three bands, thereby permitting
widespread roaming.
The signal passes through one of three SAW filters
and feed into a mixer.
An image reject mixer uses a technique similar to the
phasing method of generating a single sideband
(SSB) signal.

2.5G Cell Phone Systems







The designation 2.5G refers to a generation of cell
phones between the original second-generation (2G)
digital phones and newer third-generation (3G)
phones.
2.5G phones bring data transmission capability to 2G
phones in addition to normal voice service.
A 2.5G phone permits subscribers to exchange emails
and access the Internet by cell phone.
The two technologies used in 2.5G systems are
EDGE and GPRS.

2.5G Cell Phone Systems
(Continued)








The most popular 2.5G technology is the general
packet radio service (GPRS).
This system is designed to work with GSM phones.
It uses one or more of the eight time slots in a GSM
phone system to transmit data rather than digitized
voice.
A faster 2.5G technology is enhanced data for GSM
evolution (EDGE).
It uses 8-PSK modulation instead of GMSK to
achieve even higher data rates up to 384 kbps.

3G Cell Phone Systems






Third-generation (3G) cell phones are true packet
data phones.
3G phones feature enhanced digital voice and highspeed data transmission capability.
3G applications include fast email and Internet
access.
3G phones are being packaged with personal digital
assistants (PDAs).
High speed also permits the transmission of video.

Base Stations








The most complex and expensive part of any cellular
telephone system is the network of base stations that
carriers must have to make it all work.
Base stations consist of multiple receivers and
transmitters so that many calls can be handled on
many different channels simultaneously.
The most visible feature of a base station is its
antenna on a tower.
Base station antennas have become directional which
helps to increase subscriber capacity.

Horizontal Radiation and Reception
Pattern of a Cell Site Antenna

Wireless LANs and PANs


Local-area networks (LANs) are still interconnected
mainly by CAT5 twisted pair.



Wireless extensions and even complete wireless
LANs have become more common now that reliable,
low-cost wireless modems are available.



Wireless personal-area networks (PANs) are being
implemented in a variety of applications.

Wireless LANs








In a wireless LAN, the computers or nodes are linked
to one another by radio.
Each computer contains a sophisticated modem that
both transmits and receives over a short distance.
Each wireless node is linked back to a server that
makes the connection between different nodes.
The most robust, affordable, and flexible standard is
the 802.11b IEEE wireless Ethernet standard.
Flexibility and cost make wireless LANs so
appealing.

Wireless Gateway Using 802.11b
Wireless Ethernet

PANs and Bluetooth







A personal-area network (PAN) is a very small
network that is created informally or on an ad hoc
basis.
A PAN typically involves two or three nodes, but
some systems permit many nodes to be connected in a
small area.
PANs can be wired, but today all are wireless.
The most popular wireless PAN system is Bluetooth,
a standard developed by the cell phone company
Ericsson for use as a cable replacement.

Bluetooth







Bluetooth is a digital radio standard that uses
frequency-hopping spread spectrum (FHSS) in the
unlicensed 2.4-GHz ISM band.
Three levels of transmission power have been defined
depending upon the application.
Bluetooth transceivers are available in either one or
two chip sets that interface to the PAN.
Bluetooth transceivers send out search signals and
then listen for nearby equipped Bluetooth devices.

Bluetooth (Continued)






If another Bluetooth device comes into range the two
Bluetooth devices automatically interconnect and
exchange data.
These devices form what is called a piconet, the
linking of one Bluetooth device that serves as a
master controller to up to seven other Bluetooth slave
devices.
Bluetooth devices can also link to other piconets to
establish larger scatternets.

Bluetooth (Continued)






The main applications for Bluetooth are cordless
headsets for cell phones, wireless connections
between PCs, or laptop computers and PDAs.
Bluetooth applications include: laptop connections at
meetings, wireless printer-to-PC connections, laptopto-cell phone connections, wireless audio headsets,
and wireless digital camera-to-TV set connections.
The Bluetooth standard is maintained by the
Bluetooth Special Interest Group (SIG) and supported
by more than 2000 manufacturers.

Bluetooth Piconet with Scatternet
Link

Infrared Wireless






Perhaps the most widespread wireless system uses
infrared (IR) light for short-distance data
communication.
The most widely used is the wireless remote control
on TV sets, VCRs, and DVD players and on most
audio CD stereo systems.
Infrared has also been used for wireless LANs and
PANs.

TV Remote Control





Almost every TV set sold these days, regardless of
size or cost, has a wireless remote control.
Other consumer electronic products have remote
controls including VCRs, cable TV converters, CD
and DVD players, stereo audio systems, and some
ordinary radios.
Generic remote controls are available to hook up to
any device that you wish to control remotely.

TV Remote Control (Continued)





All remote control devices work on the same
principle.
A small handheld battery-powered unit transmits a
serial digital code via an IR beam to a receiver that
decodes it and carries out the specific action defined
by the code.
A TV remote control is one of the more sophisticated
of these controls, for it requires many codes to
perform volume control, channel selection, and other
functions.

IR PANs





Besides remote control, the primary application for
IR data communication is in short-distance links
between computers, computers and printers, or ad hoc
PANs.
Distance links are typically up to 1 m, however under
some conditions, the distance can be extended to 9 m.
There must be a clear line of sight between the
transmitter and receiver.

Common Applications for IR Data
Communication

IR PANs (Continued)





An IR transceiver connects to interface circuitry in
the PC or PDA.
The interface is typically a small embedded controller
inside the computer or PDA.
The encoder puts the serial digital data from the PC
or PDA into the proper format for transmission.
A high-current bipolar transistor or MOSFET drives
one or more IR LEDs.

IR PANs (Continued)





The receiver consists of the PIN diode that picks up the IR
light from a nearby transmitter.
The signal is amplified and shaped and then sent to the
decoder, which recovers the original data.
Although many laptops and PDAs have a built-in transceiver,
their use is often restricted by this need for line of sight.
A better arrangement is a receiver dongle which consists of a
cable attached to the interface in the PC or PDA and to the
movable dongle containing the LED and PIN diode.

IR Wireless LAN Transceiver

IrDA System





The most widely used IR data communication system
was developed by Hewlett-Packard.
It has since become an international standard that is
maintained by the Infrared Data Association (IrDA).
The complete interface and system are referred to as
IrDA.
The systems are designed for a short range of 20 to
30 cm, but can be used up to 1m.

IrDA System







Most systems use data speed rates of 4 Mbps,
however, a 16-Mbps version is now available.
IrDA does not use a modulated IR beam, but rather
baseband transmission that requires encoding and
decoding.
The standard NRZ serial data is converted into pulses
especially encoded for IR operation.
The 4-Mbps version uses another encoding scheme,
called 4 PPM (pulse position modulation).

Radio Frequency Identification





Another growing wireless technique is radio
frequency identification (FRID).
RFID uses thin, inexpensive tags or labels containing
passive radio circuits that can be queried by a remote
wireless interrogation unit.
The tags are attached to any item that is to be
monitored, tracked, accessed, located, or otherwise
identified.

Radio Frequency Identification
(Continued)






RFID tags are widely used in inventory control,
container and parcel shipping, capital equipment and
other asset management, baggage handling, and
manufacturing and production line tracking.
Other applications for RFID tags are personnel
security checking and access, animal tracking, and
theft prevention.
As the technology develops, prices drop and new
applications are being discovered.

RFID Operation





The tag is a very thin labelike device into which is
embedded a simple passive single-chip radio
transceiver and antenna.
The chip also contains a memory that stores a digital
ID code unique to the tagged item.
For the item to be identified, it must pass by the
interrogation or reader unit, or the reader must
physically go to a location near the item.

RFID Operation (Continued)






The reader unit sends out a radio signal that may travel from a
few inches up to no more than a hundred feet or so.
The radio signal is strong enough to activate the tag.
The tag rectifies and filters the RF signal into direct current
that operates the transceiver.
This activates a low-power transmitter that sends a signal back
to the interrogator unit along with its embedded ID code.
The reader checks its attached computer where it notes the
presence of the item and may perform other processing tasks
associated with the application.

RFID Components

RFID Tag Configurations

Ultrawideband Wireless






Perhaps the newest and most unusual form of
wireless is known as ultrawideband (UWB) wireless.
The primary application of UWB has been military
radar.
Also known as impulse, basband, or carrierless
wireless, UWB transmits data in the form of very
short pulses, typically less than 1 ns.
The UWB transmitter circuits use BPSK to generate
pulses which are applied directly to the antenna.

Ultrawideband Wireless
(Continued)






The receiver amplifies the incoming signal and then
applies it to a correlator consisting of a multiplier,
where it is multiplied by a stream of coded pulses
similar to those transmitted.
The multiplier output exceeds a specific level, it is
considered to be detected and recovered.
The recognized signal is then demodulated into the
original data.
Broadband antennas are used for UWB.

Advantages and Disadvantages of
UWB
UWB offers many benefits to radar, imaging, and
communication applications:





Superior resolution in radar and imaging.
Immunity to multipath propagation effects.
Higher data rates than are possible with other wireless
technologies
License-free operation

Advantages and Disadvantages of
UWB (Continued)







No interference to other signals using the same
frequency band. UWB signals appear as random
noise to conventional radios.
Power-efficient. Extremely low-power operation.
Peak power levels are in the milliwatt region, and
average power in microwatts.
Simple circuitry, most of which can be integrated in
standard CMOS.
Potentially low cost.