Transcript Slide 1

Bluetooth, IEEE 802.11 &
Cell Phone Systems
--Arun Radhakrishnan
--Thierry Fernaine
--Vipul Gautam
Overview
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What is Bluetooth?
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Specifications and Protocols
What is 802.11?
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-- Arun
Specifications and Protocols
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802.11 vs. Bluetooth
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Cellular Phone Systems
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-- Vipul
-- Thierry
CDMA
TDMA
FDMA
Generations of cell phones (1G to 4G)
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Experiments/Demonstrations
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Summary and Future Plans
Schedule
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Brainstorming the tasks involved in the project
 15th February, 2003
Information on Bluetooth and 802.11
 25th February, 2003
Analyzing Bluetooth vs 802.11
 28th April, 2003
Obtaining materials on phone systems (CDMA, TDMA, FDMA)
 23rd April, 2003
Information about 3G and 4G
 17th April, 2003
Talking to a professor about doing an experiment on wireless
 10th March, 2003
Observing the experiment performed by a TA
 2nd April, 2003
Bluetooth
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Protocol for the efficient transmission of data
Designed for devices such as cell phones,
printers, PDA’s, notebook computers, fax
machines
Bluetooth
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Low power link
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Short time data transfers
Small indoor distances
Line of Sight is not required
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Better than IR link
Bluetooth Specification Protocol Stack:
Bluetooth
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Operates in the 2.4GHz band
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Uses frequency hopping
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Unlicensed band
2.4 to 2.4385 GHz
79 hopping frequencies separated by 1 MHz
Data rate  1Mbps
Frequency Hopping
Frequency Hopping
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Characterized by its system of fast frequency hops
 10 different types of hopping sequences are
defined
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5 of the 79 MHz range/79 hop system and 5 for the
23 MHz range/23 hop system.
The different range system's hopping sequences differ
in frequency range 79MHz / 23MHz, and segment
length : 32 hops(79MHz system) / 16 hops(23MHz
system).
Frequency Hopping
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Assurance of high quality communication in large
urban centers and high-capacity networks
The millisecond rhythm with which the change of
frequency takes place enables interference to be
eliminated and prevent fading effects.
Deployed primarily in the military sector as well as in
diplomatic communications via radio due to its
unique bug-proof characteristics.
Data Layer
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Piconets are a collection of devices connected via
BT technology in an ad hoc fashion.
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Each may have as many as 8 connected devices.
One unit acts as the master and the others as slaves.
Devices create many overlapping networks called
Scatternets.
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Formed by multiple independent and non-synchronized
piconets.
Data Layer
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Master device
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Initiates an action or requests a service.
Clock and hopping sequences are used to
synchronize all other devices in the piconet.
What is 802.11
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Wireless standards that specify an interface between a wireless
client and a central point of access and among wireless clients.
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The IEEE 802.11 specifications tailored to resolve compatibility
issues between manufacturers of wireless LAN equipment.
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The original IEEE 802.11 specifications defined data rates of 1
Mbps and 2 Mbps via radio waves
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The IEEE 802.11 specifications continue to expand and new
standards are being considered and ratified. The most commonly
used wireless standard is IEEE 802.11b.
802.11 Network
802.11 a-g
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802.11a:
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802.11b:
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designed to operate in the 5 GHz band.
Achieves data transmission rates of 54Mbps.
Not readily accepted overseas.
"High Rate" standard, also known as Wi-Fi (for "wireless fidelity)
The family of IEEE 802.11b specifications allows for a wireless
data transmission
rate of 11 Mbps as an unlicensed use of the 2.4-GHz radio
frequency band.
802.11g:
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The latest wireless networking specification from IEEE
based on 802.11b.
will broaden 802.11b's data rates to 54 Mbps within the 2.4 GHz
band using OFDM (Orthogonal Frequency Division Multiplexing)
technology.
IEEE 802.11g is backward compatible with IEEE 802.11b.
802.11 protocols contd..
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Task Group "C"
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Task Group "D"
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enhance the MAC layer to improve quality of service (QoS) for time-sensitive applications like realtime voice and video.
Task Group "F"
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modifying the Physical layer to meet regulatory requirements around the globe.
Task Group "E"
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improving the MAC layer to improve bridging
improve interoperability of access points from different vendors in a distribution system.
Task Group "H"
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channel selection and transmit power issues to ensure that 802.11a is usable in Europe, similar to
what "D" is doing for 802.11b.
Some European countries currently do not allow 802.11a, favoring the European HiperLAN2 5 GHz
wireless LAN standard instead.
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Task Group "I"
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recently spun-off from Task Group "E" to put more emphasis on improving the security and
authentication mechanisms.
Motivation for 802.11
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Increased flexibility: A conference with an ad-hoc
network can be set up and dismantled in a short time.
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Increased mobility: Users can move around without
restrictions and access LANs from anywhere.
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More economical: In old buildings it is more
economical to put up some wireless stations than to
break up walls. In factories, putting wires may not be
feasible.
What is spread spectrum radio
technology?
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Increase reliability
Boost throughput
Allow many unrelated products (e.g., microwave
ovens) to share the spectrum with minimal
interference.
2 spread spectrum techniques:
Frequency hopping spread spectrum (FHSS)
 Direct sequence spread spectrum (DSSS)
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What is spread spectrum
radio technology?
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FHSS:
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DSSS:
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communicate by splitting each byte of data into several parts
sending them concurrently on different frequencies
FHSS:
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send a short burst of data
shift frequencies (hop)
send another short burst.
relatively simple radio design
but limited to speeds of no higher than 2 Mbps
leads to high amount of hopping.
DSSS:
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uses a lot of the available bandwidth, about 22 megahertz (MHz)
capable of much greater speed than FHSS since the devices can
send a lot more data at the same time.
Security
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SSID:
Each access point is associated with a SSID (service set identifier)
To access the network a client computer should be configured
with the correct SSID
MAC:
Each client computer has a unique MAC (Media Access Control)
address. Each access point is programmed with a list of MAC
addresses so it allows only those to associate with the AP.
WEP:
Wireless transmissions are easier to intercept than transmissions
over wired networks.
WEP (Wired equivalent privacy) employs the symmetric key
encryption algorithm, Ron’s Code 4 Pseudo Random Number
Generator (RC4 PRNG).
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802.11 vs. Bluetooth
Technology:
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Bluetooth uses FHSS (Frequency Hopping Spread Spectrum )
802.11 used FHSS and DSSS. Currently 802.11b uses only
DSSS for higher data transfer capability. 802.11a and 802.11g
use a Orthogonal Frequency Division Multiplexing (OFDM)
scheme in the 5 and 2.4-GHz frequency range, respectively
Coverage:
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Bluetooth covers a personal area (PAN) – the space of a room
(up to 30 feet).
802.11specifications provide coverage for local area networks
(LANs) – an office building or parts of a campus using multiple
access points (APs). Each AP has a range of up to 300 feet.
Cellular Phone Systems
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TDMA
FDMA
CDMA
Cell Phones Generations
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Specifications
Improvements
Future Plans
Frequency Division Multiple Access
(FDMA)
Frequency
Each user is assigned
one frequency to
transmit.
W Hz
User 4
User 3
Example: AMPS
User 2
User 1
Time
T sec
Time Division Multiple Access
(TDMA)
Frequency
W Hz
Time
User 1
User 2 User 3 User 4
T sec
Several users transmit at the same frequency but in
different time slots.
Example: GSM and IS-136
Used by AT&T and T-Mobile
Code Division Multiple Access
(CDMA)
• Each user transmits all the
time over all the frequency
band, but has a different
“spreading code”.
• The base station differentiates
users based on their codes.
• Example: IS-95 (cdmaOne)
Code 1
Code 2
Code 3
Code 4
• Used by Sprint and Verizon
CDMA Pros & Cons
Advantages:
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Interference rejection
Provides security / privacy
Simple to add users to system
Greater coverage with fewer cell sites
Disadvantages:
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Near-Far Problem
• Solution ?
Frequency Reuse
FDMA & TDMA
Need frequency planning
Adjacent cells  Different Frequencies
CDMA
NO need for frequency planning
Adjacent cells  Same freq.
Separated by code channels
The “Near-Far Problem”
 Nearby mobiles  strong signal
 Far away mobiles  weak signals
Power Control in CDMA
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Mobiles adjust power at which they transmit.
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Base station receives all signals at the appropriate power.
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The CDMA network independently controls the power at
which each mobile transmits.
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Extra advantage: Extended battery life
Generations of Cell Phones
AMPS: 1983
1st
Generation
GSM: 1992
IS-95: 1993
IS-136: 1996
cdma2000: 2002
WCDMA: 2002
Higher data rates for integration
of mobile multimedia services
2nd
Generation
Third Generation
Fourth Generation
Comparison of various
cellular standards
Name
Year
Originated Multiple Access
Data Rate
Introduced
From
Scheme
AMPS
1983
US
FDMA
19.2 kbps
GSM
1992
Germany
TDMA
22.8 Kbps
IS-136
1996
US
TDMA
13 Kbps
IS-95
1993
US
CDMA
19.2Kbps
cdma2000
2002
US
CDMA
up to 2.07 Mbps
WCDMA
2002
Europe
CDMA
up to 2.04 Mbps
Generations of Cell Phones
1G:
• Phones are only capable of making and receiving voice calls.
2G:
• Phones can receive and send pieces of data:
• E-mails, Web pages, etc…
• Updated versions of TDMA and CDMA allow features like caller ID and
SMS (short message service)
3G:
• Phones can receive and send both voice and data, but at speeds of
about 144kbps, which is similar to what a broadband Internet connection
offers PC users.
• Current applications under development include geo-location
capabilities using Global Positioning Systems (GPS), audio and video
streaming, and other types of entertainment.
Goals of 3G
Offer services like:
 Increased Bandwidth
 Wireless voice
 Video
 Email
 Web browsing
 Videoconferencing
Rates
• 2 Mbps in fixed
applications
• Up to 384 Kbps
when a device is
moving at pedestrian
speed
• 128 Kbps in a car
Goals of 4G
Enable mobile phones to be a combined:
 Camera
 Video camera
 Computer
 Stereo
 Radio
CDMA Experiment
Equipment:
• PN Code Generator
• Carrier Frequency
• Oscilloscope
• Antennas (Transmitter & Receiver)
• Signal source
• Computers with LAWN software
Objectives:
• Understand concept of CDMA
• Understand how PN code generator works
• Demonstrate jamming / interference
Summary
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Future for Bluetooth and 802.11
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Can they coexist?
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802.11
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Long term: Bluetooth will be built in.
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Currently: User has to choose between the two technologies.
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Bluetooth is cheap!!!
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802.11e may have been designed to combat with Bluetooth.
 Frequency hopping
 Mobile LAN access
Summary
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Cellular Phone Systems
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CDMA  wider bandwidth, power efficient, interference rejection,
security, more users. BUT … Near-Far Problem !
Solution: Power Control
TDMA  Mostly used in Europe, partially in the US (AT&T and T-Mobile)
FDMA  Previously used by AMPS (1G)
Generations of cell phones (1G to 4G)
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Higher data rates, more multimedia features available
Experiment
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PN Code generator, Frequency Jamming
References
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a, b, e, and g--What 802.11 means to me (and you, too), David Coursey, Executive
Editor, AnchorDesk
L.M. Correia and R. Prasad, “An Overview of Wireless Broadband Communication”,
IEEE Communication Magazine, Jan. 1997, pp.28-33
Naveen Chandran and Matthew C. Valenti, “Three generations of cellular wireless
systems”
http://www.qualcomm.com/
http://www-2.cs.cmu.edu/~dpwu/books/EE
Bluetooth versus 802.11, Nick Hunn, TDK Systems, www.cellular.co.za
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http://www.palowireless.com
www.10meters.com/blue_802.html maintained by Karen E. Peterson and Caroline
Scarborough
http://www.hoti.org/hoti9_tutorial.html, lecture by Pravin Bhagwat, ReefEdge Inc.
http://grouper.ieee.org/groups/802/11/main.html
http://www.utexas.edu/its/wireless/faqs/#80211
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http://www.oreillynet.com/pub/a/wireless/
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