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EE320 Telecommunications Engineering Topic 1: Propagation and Noise

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EE320 Telecommunications Engineering Topic 1: Propagation and Noise James K Beard, Ph. D. jkbeard_at_temple.edu E&A 349 http://astro.temple.edu/~jkbeard/ – PowerPoint PPT presentation

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Title: EE320 Telecommunications Engineering Topic 1: Propagation and Noise


1
EE320 Telecommunications EngineeringTopic 1
Propagation and Noise
  • James K Beard, Ph. D.
  • jkbeard_at_temple.edu
  • EA 349
  • http//astro.temple.edu/jkbeard/

2
Essentials
  • Text Simon Haykin and Michael Moher, Modern
    Wireless Communications
  • Prerequisites
  • Analog and Digital Communication EE300
  • Analog and Digital Communication Laboratory
    EE301
  • SystemView
  • Web Site
  • URL http//astro.temple.edu/jkbeard/
  • Content includes slides for EE320 and EE521
  • SystemView page
  • A few links
  • Office Hours
  • EA 349
  • Hours Tuesday afternoons 300 PM to 430 PM
  • MWF 1030 AM to 1130 AM

3
Topic 1 Subjects
  • Course objectives
  • Course Summary and Topics
  • Essential Technologies
  • Introduction to Communications
  • History
  • Concepts
  • Propagation
  • Free space
  • Local propagation effects
  • Noise and interference
  • Thermal noise
  • Man-made noise
  • Link calculations

4
EE320 Topic 1
  • Course Objectives, Summary and Topics

5
Course Objectives
  • Objectives
  • Identify
  • Concepts of pass band coherent and non-coherent
    modulation systems
  • Societal and global issues in communication
    regulatory affairs
  • Apply Principles
  • 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
  • http//www.temple.edu/ece/ee320.htm

6
Course Summary
  • Fourteen weeks of classes
  • Two in-progress exams, one final exam
  • In-progress on 5th and 9th weeks, 20 of grade
  • Final on fifteenth week, 40 of grade
  • Individually assigned project
  • Assigned in fifth week
  • Execute your project in SystemView
  • 40 of grade
  • Deductions from final grade
  • 0.5 for each unexcused absence
  • 1 for each missed 10 minute Pop Quiz response

7
Course Topics (1 of 2)
  • Propagation and Noise
  • Modulation
  • FDMA
  • Pulse shading, power spectra, and FDMA
  • Bit Error Rate
  • Coding
  • Information theory, and convolutional codes
  • Maximum likelihood decoding
  • Noise performance
  • TDMA

8
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

9
EE320 Topic 1
  • Introduction to Communications

10
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

11
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

12
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

13
Communications Overview
  • Conceptual layers
  • Physical layer the channel
  • Data link layer input and output
  • Network layer routing
  • 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

14
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 data rate
  • The error rate
  • The conditions for success of communications
  • Usage of the communications

15
Examples
  • Systems
  • Public switched telephone network
  • Internet
  • Physical layer Modem, transmitter, medium
  • Data link layer EDAC, grid, multiplexing
  • Network layer grid routing, flow control

16
The Physical Layer
  • Transmitter, channel, receiver
  • Channel may be
  • Open RF
  • Beamed RF
  • Cable or fiber optic
  • Other such as satellite links
  • Any combination of these

17
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

18
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

19
Functional Summary
  • The layers
  • The physical layer is the transmitter-channel-rece
    iver
  • The data link layer is the information encoding
    and decoding
  • The network layer is the routing through the
    physical layer
  • The engineers 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

20
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

21
EE320 Topic 1
  • Propagation and the RF link budget

22
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

23
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

24
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

25
Transmit Antenna
Power density
R
Transmitter Power
26
Receive Antenna
Receive effective area
Incident power density
27
Received Power
  • Combining the equations
  • We will derive the more common form

We need the gain equations
28
Directivity and Gain
  • Whats the difference?
  • Directivity is the radiated power density in a
    specific direction
  • Gain is the directivity with the losses included
  • Conventionally speaking
  • Usually we speak of the maximum peak gain
  • Losses are the ohmic or heating losses

29
Transmit Effective Area
  • The total power radiated is
  • The transmit directivity can be posed as

30
Receive Antenna Gain
  • The average effective transmit area is
  • From electromagnetic theory, this is always

31
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

32
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

33
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
  • This completes our derivation

34
Antenna Efficiency
  • Applicability
  • Reflectors, planar arrays, arrays of dipoles or
    loops
  • The antenna efficiency is defined as
  • Efficiency is always less than 1
  • Causes for lower efficiency are
  • Non-uniform illumination
  • Spill-over of reflectors
  • Edge effects and losses on reflection and in horns

35
SummaryFree Space Modeling
  • An isotropic transmitter produces a power density
    at the receiver
  • Power received at an antenna of effective area Ae
    in Watts

Polarization is considered later
36
Local Propagation Effects
  • Two types of mobile radio
  • Portable stationary during communicatoins
  • Mobile moving during communications
  • Fading
  • Slow refraction changes in the RF path
  • Fast path changes as radio moves
  • Doppler
  • Fast fading the picket fence

37
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

38
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

39
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
    chi-square distribution
  • This is the effective result when a direct path
    signal is added to a scattered signal

40
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

41
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

42
Noise and Interference
  • Thermal noise in the receiver
  • Background noise
  • Earths radiation
  • Man-made
  • Each element of a receiver adds noise

43
Thermal Noise
  • Equilibrium of RF energy with thermal energy
    provides a noise background with a power spectral
    density of
  • Quantum theory shows that it rolls off after 1000
    GHz

44
Earths 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

45
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

46
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

47
Antenna Noise Figure
  • Inputs are Earths radiation and other ambient
  • Plumbing and resistive losses often increase the
    antenna noise figure in the real world

48
Cascaded Elements
  • System noise temperature for two cascaded
    elements is
  • Including the antenna and more elements

49
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
  • Path is more complex fading, reflection losses
  • Ranges much shorter

50
The Communications Equation
51
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
  • Often done in tables with quantities in dB

52
Local Propagation Effects
  • Two types of mobile radio
  • Portable stationary during communicatoins
  • Mobile moving during communications
  • Fading
  • Slow refraction changes in the RF path
  • Fast path changes as radio moves
  • Doppler
  • Fast fading the picket fence

53
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

54
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

55
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
    chi-square distribution
  • This is the effective result when a direct path
    signal is added to a scattered signal

56
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

57
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

58
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

59
See Spreadsheets
  • Example 2.20
  • According to example
  • Details explained
  • Problem 2.20
  • Modify paramters as given
  • Availabilty Gaussian PDF(0.675) 0.75

60
Example 2.20
61
Problem 2.22
62
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

63
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

64
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
    0-442-01592-5
  • R.S. Elliot, Antenna Theory and Design, IEEE
    classic reissue, ISBN 0-471-44996-2

65
Summary
  • Course summary
  • Organization and grading
  • Topics
  • Result
  • Design concepts for communication networks
  • Execute a term project in SystemView
  • Overview of communication
  • Physical layer Transmitter, channel, receiver
  • Data link layer FDMA/TDMA/CDMA/SDMA
  • Network layer routing, QoS
  • Free space propagation
  • Introduction to antenna concepts

66
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

67
Text and Assignment
  • Text
  • Simon Haykin and Michael Moher, Modern Wireles
    Communicatinons ISBN 0-13-022472-3
  • SystemView User's Manual, Elanix, Inc
  • http//www.elanix.com/
  • http//www.elanix.com/pdf/SVUGuide.pdf
  • Assignment Read Text
  • Chapter 1
  • Chapter 2,2.2, 2.6, 2.8, 2.9
  • Look at TUARC
  • K3TU, websites
  • http//www.temple.edu/ece/tuarc.htm
  • http//www.temple.edu/k3tu

68
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
    0-442-01592-5
  • R.S. Elliot, Antenna Theory and Design, IEEE
    classic reissue, ISBN 0-471-44996-2
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