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
7/21/2015
Week 1
3
EE320 Topic 1
Course Objectives, Summary
and Topics
7/21/2015
Week 1
4
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
Week 1
5
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


7/21/2015
0.5% for each unexcused absence
1% for each missed 10 minute Pop Quiz response
Week 1
6
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
7/21/2015
Week 1
7
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
7/21/2015
Week 1
8
EE320 Topic 1
Introduction to
Communications
7/21/2015
Week 1
9
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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10
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
7/21/2015
Week 1
11
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
7/21/2015
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12
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
7/21/2015
Week 1
13
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
7/21/2015
Week 1
14
Examples

Systems
 Public
switched telephone network
 Internet
Physical layer: Modem, transmitter,
medium
 Data link layer: EDAC, grid, multiplexing
 Network layer: grid routing, flow control

7/21/2015
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15
The Physical Layer
Information
Source
Information
Sink
Transmitter


Channel
Receiver
Transmitter, channel, receiver
Channel may be





7/21/2015
Open RF
Beamed RF
Cable or fiber optic
Other such as satellite links
Any combination of these
Week 1
16
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
7/21/2015
Week 1
17
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
7/21/2015
Week 1
18
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
7/21/2015
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19
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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20
EE320 Topic 1
Propagation and the RF link
budget
7/21/2015
Week 1
21
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
7/21/2015
Week 1
22
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
7/21/2015
Week 1
23
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

7/21/2015
Week 1
24
Transmit Antenna
Power
density
PER

2
4  R
R
Transmitter
Power P
ER
7/21/2015
Week 1
25
Receive Antenna
Incident
power
density
Receive
effective
area ArRcv

PRcv    AeRcv
7/21/2015
Week 1
26
Received Power

Combining the equations
PRcv

PER  AeRcv

4  R 2
We will derive the more common form
PRcv 
7/21/2015
PT  GTr  GRcv  
2
4


R
 
2
Week 1
2
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
7/21/2015
Week 1
28
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
7/21/2015
Week 1
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
7/21/2015
Week 1
30
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
7/21/2015
Week 1
31
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
7/21/2015
Week 1
2
32
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
7/21/2015
Week 1
33
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



7/21/2015
Non-uniform illumination
Spill-over of reflectors
Edge effects and losses on reflection and in horns
Week 1
34
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
7/21/2015
Week 1
35
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
36
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
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
7/21/2015
Week 1
38
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
39
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

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
7/21/2015
Week 1
41
Noise and Interference
Thermal noise in the receiver
 Background noise

 Earth’s
radiation
 Man-made

Each element of a receiver adds noise
7/21/2015
Week 1
42
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
7/21/2015
Week 1
43
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
7/21/2015
Week 1
44
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

7/21/2015
Week 1
45
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
7/21/2015
Week 1
46
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
7/21/2015
Week 1
47
Cascaded Elements

System noise temperature for two
cascaded elements is
T1 2

T2
 T1 
G1
Including the antenna and more elements
TSYS
7/21/2015
T3
T2
 TA  T1  

G1 G1  G2
Week 1
48
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
7/21/2015
Week 1
49
The Communications Equation
PTr  GTr  GRcv
PR

N0 LPath  k  TSystem
7/21/2015
Week 1
50
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
7/21/2015
Week 1
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
7/21/2015
Week 1
57
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
7/21/2015
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58
See Spreadsheets

Example 2.20
 According
to example
 Details explained

Problem 2.20
 Modify
paramters as given
 Availabilty: Gaussian PDF(0.675) = 0.75
7/21/2015
Week 1
59
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
Week 1
60
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
Week 1
61
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
7/21/2015
Week 1
62
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
7/21/2015
Week 1
63
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
7/21/2015
Week 1
64
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
7/21/2015
Week 1
65
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
7/21/2015
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
Week 1
67
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
Week 1
68