Transcript Document
EE320 Telecommunications
Engineering
Topic 1: Propagation and
Noise
James K Beard, Ph. D.
[email protected]
E&A 349
http://astro.temple.edu/~jkbeard/
7/21/2015
Week 1
1
Essentials
Text: Simon Haykin and Michael Moher, Modern
Wireless Communications
Prerequisites
Web Site
Analog and Digital Communication: EE300
Analog and Digital Communication Laboratory: EE301
SystemView
URL http://astro.temple.edu/~jkbeard/
Content includes slides for EE320 and EE521
SystemView page
A few links
Office Hours
7/21/2015
E&A 349
Hours Tuesday afternoons 3:00 PM to 4:30 PM
MWF 10:30 AM to 11:30 AM
Week 1
2
Topic 1 Subjects
Course objectives
Course Summary and Topics
Essential Technologies
Introduction to Communications
Propagation
Free space
Local propagation effects
Noise and interference
History
Concepts
Thermal noise
Man-made noise
Link calculations
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3
EE320 Topic 1
Course Objectives, Summary
and Topics
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Course Objectives
Objectives
Identify
Apply Principles
Concepts of pass band coherent and non-coherent modulation systems
Societal and global issues in communication regulatory affairs
Angle modulation and demodulation to send and receive information
Random processes to analyze the source and magnitude of error in
information reception
Signal analysis to optimal and efficient modulation systems
Information theory to improve the performance of digital communication
systems
See Temple course web site for more information
7/21/2015
http://www.temple.edu/ece/ee320.htm
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Course Summary
Fourteen weeks of classes
Two in-progress exams, one final exam
Individually assigned project
In-progress on 5th and 9th weeks, 20% of grade
Final on fifteenth week, 40% of grade
Assigned in fifth week
Execute your project in SystemView
40% of grade
Deductions from final grade
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0.5% for each unexcused absence
1% for each missed 10 minute Pop Quiz response
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Course Topics (1 of 2)
Propagation and Noise
Modulation
FDMA
Pulse shading,
Bit Error Rate
power spectra, and FDMA
Coding
Information
theory, and convolutional codes
Maximum likelihood decoding
Noise performance
TDMA
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Course Topics (2 of 2)
Spread spectrum
CDMA
Direct-sequence
modulation
Spreading codes and orthogonal spreading factors
Gold codes
Code synchronization
Power control
Frequency hopping and spread spectrum
Wireless architectures
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EE320 Topic 1
Introduction to
Communications
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Essential Technologies
Probability and Statistics
Behavior
of channel over time
Description and behavior of noise
Signals and systems
Time
and frequency domain signal and chanel
characterization
Prediction and modeling of communications
Coding, modulation, and demodulation
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Introduction
History of telecommunications
Communications overview
Layers
Concepts
The conceptual layers
Physical
layer, transmitter/receiver and channel
Data link layer, our primary focus
Netework layer, infrastructure
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History
1864 – Maxwell predicted radio waves
1887 – Hertz demonstrated radio waves
1897 – Lodge demonstrated wireless communications
1901 – Marconi demonstrated transatlantic communications
1903 – DeForest demonstrated first vacuum tube amplifier
1906 – Fessenden started first AM radio station
1927 – First TV broadcasts
1947 – Microwave relay from Boston to NYC
1947 – Bell Labs announced the transistor
1955 – TI announced production silicon transistors
1958 – First satellite voice channel
1981 – First cell phone system, in Scandinavia
1988 – First digital cell phone system in Europe
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Communications Overview
Conceptual layers
layer – the channel
Data link layer – input and output
Network layer – routing
Physical
Concepts
Given
the channel, or bandwidth
Determine the coding and multiplexing, or tuning or
time multiplexing and codes
Route the data through the nodes to the receiver
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The Conceptual Layers
The physical layer is the channel
The data link layer is the information input and
output
The network layer routes the input and output
data
Together they determine
The
The
The
data rate
error rate
conditions for success of communications
Usage of the communications
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Examples
Systems
Public
switched telephone network
Internet
Physical layer: Modem, transmitter,
medium
Data link layer: EDAC, grid, multiplexing
Network layer: grid routing, flow control
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The Physical Layer
Information
Source
Information
Sink
Transmitter
Channel
Receiver
Transmitter, channel, receiver
Channel may be
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Open RF
Beamed RF
Cable or fiber optic
Other such as satellite links
Any combination of these
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The Data Link Layer
Highest conceptual level is the multiple access
strategy
Allows multiple users to share a channel
Frequency division multiple access (sub-channels)
Time division multiple access (time slots)
Code
division multiple access (spread spectrum)
Space division multiple access (beams)
Objective
Maximize number of users for a fixed spectrum
FDMA/TDMA/CDMA/SDMA can be layered
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The Network Layer
Determines the routing of the information
Selection
of path through available nodes
Selection of open band
Selection of unused code or time slot
Selection of unused beam
Selection of path through multiple-node network
Quality of service (QoS)
Keep
a channel open for new calls
Plan reserves for rollover for mobile netowrks
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Functional Summary
The layers
The
physical layer is the transmitter-channel-receiver
The data link layer is the information encoding and
decoding
The network layer is the routing through the physical
layer
The engineer’s perspective
The
physical layer is defines the available channel
The data link layer is the radio or user set
The network layer is the routing infrastructure
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Discussion
What are the differences in the physical
layer between
Cable
such as telephone and Ethernet
Wireless
Discuss the time variation in
The
medium
The data path
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EE320 Topic 1
Propagation and the RF link
budget
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Propagation and Noise
Text Chapter 2
2.2,
Free-Space Propagation
2.6, Local Propagation Effects
2.8, Noise and Interference
2.9, Link Calculations
Simple equations
Signal
power in the receiver
Noise in the receiver
Characterize the channel
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Free-Space Propagation
Definition
Line
of sight
Point to point
No reflections or scattering
Everything is simple and linear
Modeling
Transmitter,
antennas, and gain
Simple electromagnetic propagation
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Concepts
Transmitting power
The receiving antenna as a capture area
The isotropic (omnidirectional) antenna
and directional antennas with gain
Spreading loss
Simple equation for received power
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Transmit Antenna
Power
density
PER
2
4 R
R
Transmitter
Power P
ER
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Receive Antenna
Incident
power
density
Receive
effective
area ArRcv
PRcv AeRcv
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Received Power
Combining the equations
PRcv
PER AeRcv
4 R 2
We will derive the more common form
PRcv
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PT GTr GRcv
2
4
R
2
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We need the gain
equations
27
Directivity and Gain
What’s the difference?
Directivity
direction
Gain
is the radiated power density in a specific
PER ,
DTr ,
PTr
is the directivity with the losses included
Conventionally speaking
Usually
we speak of the maximum peak gain
Losses are the ohmic or heating losses
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Transmit Effective Area
The total power radiated is
1
PTr
2
4 R
2
PER , R 2 cos d d
2
The transmit directivity can be posed as
PER , AeTr ,
DTr ,
PTr
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ATr
29
Receive Antenna Gain
The average effective transmit area is
1
ATr
4
2
A , cos d d
Tr
2
From electromagnetic theory, this is
always
2
A
4
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The Isotropic Antenna
An idealized theoretical concept
Based on a unipole concept
Antennas
are coupling to free space from
voltage and current
Antenna design maximizes energy transfer
All antennas are circuits (loops), dipoles,
ground surfaces, or some combination of
these
A unipole cannot exist in nature
But, it is useful as a theoretical concept
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Small Antennas
Small dipoles and loaded whips
Essentially isotropic
Used on
Cell phones
Pagers
Portable
RF equipment where size is more important
than gain
Theoretical Minimum effective antenna area is
A
, PR PT
4
R
2
AISOTROPIC
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Antenna Gain
Given as peak power ratio
Power received relative to that of an isotropic
(small, omnidirectional) antenna
A function of direction from which the signal is
coming – varies as Ae
G
Ae
AISOTROPIC
4 Ae
2
4 A
2
This completes our derivation
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Antenna Efficiency
Applicability
Reflectors, planar arrays, arrays of dipoles or loops
The antenna efficiency is defined as
Rcv
AeRcv
ARcv
Efficiency is always less than 1
Causes for lower efficiency are
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Non-uniform illumination
Spill-over of reflectors
Edge effects and losses on reflection and in horns
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Summary:
Free Space Modeling
An isotropic transmitter produces a power
density at the receiver
PER ,
Rcv
Watts per square meter
2
4 R
Power received at an antenna of effective
area Ae in Watts
PER ,
PRcv Rcv AeRcv
AeRcv Polarization is
2
4 R
considered later
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Local Propagation Effects
Two types of mobile radio
– stationary during communicatoins
Mobile – moving during communications
Portable
Fading
– refraction changes in the RF path
Fast – path changes as radio moves
Slow
Doppler
Fast fading – the picket fence
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Basic Physics of Fading
The path length is a large number of
wavelengths
Received power nearly always arrives through
more than one path
The amplitudes and phases of the received
signals are all different
The sum of the received signals exhibits
amplitude changes characterized as fading
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37
Rayleigh Fading
The Rayleigh distribution
Is
the distribution of the amplitude of a complex
Gaussian random variable – or Gaussian RF noise
Mathematical statisticians call the distribution of the
squared amplitude chi-square with two degrees of
freedom
This is an effective result for received signal
power when the received signal is from a large
number of paths – a scattered signal
Time variation produces fading with amplitude
having a Rayleigh distribution
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Rician Fading
The Rician distribution
Results
from the amplitude of a constant plus
complex Gaussian noise
Mathematical statisticians call the distribution
of the squared amplitude the non-central chisquare distribution
This is the effective result when a direct
path signal is added to a scattered signal
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Doppler
A change of path length results in a
corresponding change in the number of
wavelengths between transmitter and
receiver
The frequency change is the rate of path
length change in wavelengths
f R fT
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R
40
Numerical Example
Air traffic control
Frequency
about 128 MHz
Wavelength about 2.34 meters
Aircraft velocity
About
500 kph or 310 mph
Or, 140 meters per second
Doppler frequency shift
Maximum
of 59 Hz
Decreased by cosine of angle between velocity vector
and the line of sight
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Noise and Interference
Thermal noise in the receiver
Background noise
Earth’s
radiation
Man-made
Each element of a receiver adds noise
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Thermal Noise
Equilibrium of RF energy with thermal
energy provides a noise background with
a power spectral density of
N0 k T
Quantum theory shows that it rolls off after
1000 GHz
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Earth’s Radiation
Black body radiation
Noise temperature usually considered to
be 290 K
Noise temperature can be higher
Sunlit
areas
Backlit clouds
Large hot surfaces such as parking lots
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Man-Made Noise
Sources include
Power
lines
Broadcasting and other communications,
radar
HID (mercury, xenon, neon) lights
Car and truck engine ignition systems
Spurious emissions – motor brushes, arcing…
Most significant below 100 MHz
About 40 dB over Earth radiation
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Noise Figure
Noise figure is
The
system noise level referred back to the receiver
input
Divided by baseline or reference noise from a power
spectral density of N0
Antenna noise figure is basis
System or element noise temperature is 270 K
times the noise figure
Each element of the receiver increases the
overall noise figure
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Antenna Noise Figure
Inputs are Earth’s radiation and other
ambient
Plumbing and resistive losses often
increase the antenna noise figure in the
real world
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Cascaded Elements
System noise temperature for two
cascaded elements is
T1 2
T2
T1
G1
Including the antenna and more elements
TSYS
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T3
T2
TA T1
G1 G1 G2
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Link Calculations
The communications equation
Signal
from transmitter to receiver
Noise in receiver
Summarized as SNR in receiver
Satellite systems
Simple
free-space calculations
Very long range
Terrestial systems
is more complex – fading, reflection losses…
Ranges much shorter
Path
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The Communications Equation
PTr GTr GRcv
PR
N0 LPath k TSystem
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Grouping of Terms
Communications engineering groups
terms in the communications equation
Carrier to noise density ratio is received
signal power to noise power density ratio
Others
G
EIRP PT GT , G / T
R
TSystem
Often done in tables with quantities in dB
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51
Local Propagation Effects
Two types of mobile radio
– stationary during communicatoins
Mobile – moving during communications
Portable
Fading
– refraction changes in the RF path
Fast – path changes as radio moves
Slow
Doppler
Fast fading – the picket fence
7/21/2015
Week 1
52
Basic Physics of Fading
The path length is a large number of
wavelengths
Received power nearly always arrives
through more than one path
The amplitudes and phases of the
received signals are all different
The sum of the received signals exhibits
amplitude changes characterized as
fading
7/21/2015
Week 1
53
Rayleigh Fading
The Rayleigh distribution
Is
the distribution of the amplitude of a complex
Gaussian random variable – or Gaussian RF noise
Mathematical statisticians call the distribution of the
squared amplitude chi-square with two degrees of
freedom
This is an effective result for received signal
power when the received signal is from a large
number of paths – a scattered signal
Time variation produces fading with amplitude
having a Rayleigh distribution
7/21/2015
Week 1
54
Rician Fading
The Rician distribution
Results
from the amplitude of a constant plus
complex Gaussian noise
Mathematical statisticians call the distribution
of the squared amplitude the non-central chisquare distribution
This is the effective result when a direct
path signal is added to a scattered signal
7/21/2015
Week 1
55
Doppler
A change of path length results in a
corresponding change in the number of
wavelengths between transmitter and
receiver
The frequency change is the rate of path
length change in wavelengths
f R fT
7/21/2015
Week 1
R
56
Numerical Example
Air traffic control
Frequency
about 128 MHz
Wavelength about 2.34 meters
Aircraft velocity
About
500 kph or 310 mph
Or, 140 meters per second
Doppler frequency shift
Maximum
of 59 Hz
Decreased by cosine of angle between velocity vector
and the line of sight
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Log Normal Fading
Example 2.20 on pages 80 and 81
Problem 2.22
Text 2.13, Summary
Summary
of Chapter 2, Propagation and
Noise
Pages 94-95
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See Spreadsheets
Example 2.20
According
to example
Details explained
Problem 2.20
Modify
paramters as given
Availabilty: Gaussian PDF(0.675) = 0.75
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Example 2.20
Parameter
Base station transmitter
Transmit frequency
Wavelength
Transmit power
Transmit Antenna gain
Transmit EIRP
P0 = PR at 1 meter range
Losses
Path-loss exponent (Table 2.1)
Range
Median path loss
Log normal shadowing sigma
Availability
Standard deviation factor
Shadowing margin
Units
MHz
meters
dBW
dBi
dBW
dBm
km
dB
dB
dB
Value
705
0.425238
15
2
17
17.58843
Comments
Finds P0 = power in isotropic receiver 1 meter away
Mobile public safety band
lambda = c/frequency
Transmit power of 32 W
Uniform radiation in azimuth
EIRP of 50 W, well below limit of 1000 W
P0=(EIRP/(4*pi*R0^2))*A0 in dBm, R0 = 1 meter
2.4
10
96
8
0.95
1.644853
13.15883
Based on 2.4, Terrestial Propagation Stat. Models
Applicable at edge of coverage
Range at edge of coverage
2.4 X 10 X log(R/R0), R0 = 1 meter = .001 km
Standard deviation of log-normal shadowing
Probability of path loss less than margin
NORMSINV(availability) = standard deviation factor
For 95% availablilty, 1.65 X sigma
Received Signal
GR = Receive antenna gain
PR = Received signal strength
dBi
dBm
From P0 minus losses, plus receiver antenna gain
1.5 Vertically polarized whip antenna
-90.07039 PR=P0+GR-(Median path loss)-(Shadowing margin)
Receiver characteristics
Required C/N0
Boltzmann's constant
k*T0, T0=290 K
NF = Receiver noise figure
S = Receiver sensitivity
dB-Hz
dBm-K
dBm
dB
dBm
69.8
-198.5992
-173.9752
6
-98.17518
Margin
dB
7/21/2015
Completes link equation, subtracts required C/N0
From modem specifications
1.38065 X 10^(-20) mw/K
About 4 X 10^(-18)
From receiver specifications
S=(C/N0)+(NF)+(k*T0), T0=290 K
8.104791 Margin = PR - S
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Problem 2.22
Parameter
Base station transmitter
Transmit frequency
Wavelength
Transmit power
Transmit Antenna gain
Transmit EIRP
P0 = PR at 1 meter range
705
0.425238
15
2
17
17.58843
Comments
Finds P0 = power in isotropic receiver 1 meter away
Mobile public safety band
lambda = c/frequency
Transmit power of 32 W
Uniform radiation in azimuth
EIRP of 50 W, well below limit of 1000 W
P0=(EIRP/(4*pi*R0^2))*A0 in dBm, R0 = 1 meter
dB
3.5
2
115.536
10
0.25
-0.67449
-6.744895
Based on 2.4, Terrestial Propagation Stat. Models
Applicable at edge of coverage
Range at edge of coverage
2.4 X 10 X log(R/R0), R0 = 1 meter = .001 km
Standard deviation of log-normal shadowing
Probability of path loss less than margin
NORMSINV(availability) = standard deviation factor
For 75% availablilty, 0.675 X sigma
Received Signal
GR = Receive antenna gain
PR = Received signal strength
dBi
dBm
From P0 minus losses, plus receiver antenna gain
1.5 Vertically polarized whip antenna
-89.70272 PR=P0+GR-(Median path loss)-(Shadowing margin)
Receiver characteristics
Required C/N0
Boltzmann's constant
k*T0, T0=290 K
NF = Receiver noise figure
S = Receiver sensitivity
dB-Hz
dBm-K
dBm
dB
dBm
69.8
-198.5992
-173.9752
6
-98.17518
Margin
dB
Losses
Path-loss exponent (Table 2.1)
Range
Median path loss
Log normal shadowing sigma
Availability
Standard deviation factor
Shadowing margin
7/21/2015
Units
MHz
meters
dBW
dBi
dBW
dBm
km
dB
dB
Value
Completes link equation, subtracts required C/N0
From modem specifications
1.38065 X 10^(-20) mw/K
About 4 X 10^(-18)
From receiver specifications
S=(C/N0)+(NF)+(k*T0), T0=290 K
8.472464 Margin = PR - S
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Spreadsheet
Format
Tables
similar to Table 2.3, Table 2.5
Built-in functions provide dB, Gaussian PDF
Flexibility
Easily
modified by changing one or more
parameters
Example is our example and problem
Example_2_20_page_80.xls
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Summary
Overview of telecommunications
Conceptual
layers
Free space link computations
Noise and fading
The link equations
Result
Completion
of first-pass overview
Next time: Modulation and FDMA
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Text and Assignment
SystemView User's Manual, Elanix, Inc
Look
at using SystemView in the problems for
Chapter 2
Assignment: Read text
Chapter
3, sections 3.1, 3.2, 3.3, 3.4.1, 3.7.3/4/5, 3.8,
3.12
Antenna references
Lo
and Lee, Antenna Handbook, Vol. 1, ISBN 0-44201592-5
R.S. Elliot, Antenna Theory and Design, IEEE classic
reissue, ISBN 0-471-44996-2
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Summary
Course summary
Organization and grading
Topics
Result
Design concepts for communication networks
Execute a term project in SystemView
Overview of communication
Physical layer:
Data link layer:
Transmitter, channel, receiver
FDMA/TDMA/CDMA/SDMA
Network layer: routing, QoS
Free space propagation
Introduction to antenna concepts
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Summary
Overview of communication, continued
Introduction
to antenna concepts,
continued
Antenna gain and directivity
Noise and fading
The link equations
Result
Completion
of first-pass overview
Next Topic: Modulation
and FDMA
Week 1
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66
Text and Assignment
Text
Simon Haykin and Michael Moher, Modern Wireles
Communicatinons ISBN 0-13-022472-3
SystemView User's Manual, Elanix, Inc
Assignment: Read Text
http://www.elanix.com/
http://www.elanix.com/pdf/SVUGuide.pdf
Chapter 1
Chapter 2,2.2, 2.6, 2.8, 2.9
Look at TUARC
K3TU, websites
7/21/2015
http://www.temple.edu/ece/tuarc.htm
http://www.temple.edu/k3tu
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Text and Assignment
SystemView User's Manual, Elanix, Inc
Look
at using SystemView in the problems for
Chapter 2
Assignment: Read text
Chapter
3, sections 3.1, 3.2, 3.3, 3.4.1, 3.7.3/4/5, 3.8,
3.12
Books
Lo
and Lee, Antenna Handbook, Vol. 1, ISBN 0-44201592-5
R.S. Elliot, Antenna Theory and Design, IEEE classic
reissue, ISBN 0-471-44996-2
7/21/2015
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68