welcome to
DESCRIPTION
Welcome to. Simulation of communication systems (DT001A). [email protected] and [email protected]. A project course about MATLAB with SIMULINK and Communications Blockset. MATLAB = Matrix Laboratory. - PowerPoint PPT PresentationTRANSCRIPT
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A project course about MATLAB with SIMULINK and Communications Blockset
MATLAB = Matrix Laboratory.Tool for numerical calculation and visualization. Commonly used for simulation of the communication system physical layer, signal and image processing research, etc.
SIMULINK: Toolbox in Matlabthat allows graphical data-flow oriented programming.
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Aim of the course To prepare the student for thesis project and work in the
area of telecommunciations development and research. To give experience of performance analysis of communication
systems and algorithms, at the physical layer and datalink layer.
To give experience of simulation tools such as MATLAB and SIMULINK.
This may include modelling and simulation of traffic sources, channel models, modulation schemes, error coding schemes, equalizers, algorithms and protocols.
A real-world project is studied within an application area such as cellular communications, modems for broadband access, wireless networks, short-range communication, digital TV transmission, IP-TV or IP-telephony.
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Prerequisites Computer Networks A 7.5 ECTS credits or similar Computer Engineering B, Wireless Internet access (most
important!) Computer Engineering AB-level, 30 ECTS credits TCP/IP networking Mathematical statistics Programming
Other helpful courses: Transform theory, 7.5 ECTS credits. Electrical engineering A, Analog electronics or Circuit theory Electrical Engineering B, Telecommunications, 7.5 ECTS credits. Electrical engineering B, Signals and systems, 7.5 ECTS credits. Markov processes/Queueing theory
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Litterature
Matlab and Simulink documentation will be provided electronically.
Please repeat physical layer issues and datalink layer issues in basic books in Computer Networks and Wireless Internet Access.
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Requirements
All lectures and supervision lessons are mandatory. You are expected to devote 20 hours/week to this
course, for example in L209. Quzzes (multiple choice tests): At least 70% correct
answers. Lab: About 20 hours of work. Homework problem. Oral presentations. Project
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Requirements on the project Review at least one research paper, and describe some standard and
some existing simulation model. Simulate a communications standard, or check the simulations made
in a research paper. At least modify an existing simulation model, for exampel a Simulink
or Matlab demo, or build a model of your own (more difficult) Produce some plots for several parameter cases, showing for
example BER, bit rate or delay as function of at least two different parameters, for example SNR, facing model, modulation scheme, etc.
The simulation results should be stable (the plots smooth and not jerky), i.e simulate sufficiently long simulation time, or take the average of sufficiently large number of simulations.
Draw some interesting conclusions from this.
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Grading is based on
Keeping deadlines.
Quzzes.
Showing good understanding when andwering questions from teachers and other students about your presentations.
Extent of own code.
Research relevance.
Own new results or conclusions.
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Time plan and deadlines (prel) Week 44-45 - Introduction lectures - Start lab: Intro to Simulink. (About 20 hours of work) - Electronic quizzes in webct
- Choose a standard and en existing model to simulate Week 46 - Assignment 1 (homework problem).
- Conclude lab (demonstrate to teachers) Week 47-48 - Present chapter 2 for class: Theory study – present a standard and review a research paper - Present chapter 3 for class: Model – present an existing
simulation model
Week 49-50 - Demonstrate chapter 1 to teachers: Introduction (goal of your project)
- Demonstrate chapter 4: Modifications to an existing simulation model, or a new model that you have built.
Week 51-02 - Demonstrate some simulation results to teachers. Week 03 - Final report and project presentations, incl chapter 5:
Results, and chapter 6: Conclusions.
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”IMRaD” report disposition
Use MIUN template for technical reports.
Abstract Table of contents. 1. Introduction 2. Theory study (describe a standard and review a research
paper) 3. Existing simulation model 4. Modifications to the simulation model/own simulation model 5. Simulation results 6. Conclusions List of sources Appendix: Simulation code
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Assignment 1: Theory repetition The first assignment consists of old exam problems in
Computer Networks A, Wireless Internet access B and Telecommunications B.
Deadline: At the supervision lesson week 45. Be
prepared to present your answers on the whiteboard.
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MATLAB
MATLAB = Matrix Laboratory.Tool for numerical calculation and visualization. Commonly used for simulation of the communication system physical layer, signal and image processing research, etc.
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Command window
Workspace
Commandhistory
This is how MATLAB looks like
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More MATLAB windows
Figure window
M-file editor
Array editor
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How to get help in MATLAB?help functionsname
Shows unformatted text
doc funktionsnamn
Shows HTML documentation in a browser
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SIMULINK
SIMULINK: Toolbox in Matlabthat allows graphical data-flow oriented programming.
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Repetition of some basic concepts Frequency spectrum Digitalisation, source coding Error coding Modulation Multiple-access methods Base-band model Distorsion, noise Signal-to-noise ratio Bit-error ratio Statistics
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Repetition of some basic concepts
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Digitalization
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PCM = Pulse Code Modulation = Digital transmission of analogue signals
SamplerAD-converter
with seerial output
011011010001...
DA-converter
Anti aliasing-filter
Interpolationfilter
Number exemples from PSTN = the public telephone network
300-3400Hzband pass
filter. Stopseverything
over 4000Hz.
8000sampelsper sec
8 bit per sampeli.e. 64000 bpsper phone call
28 = 256voltage levels
0
1
Microphone Loudspeaker
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Aliasing
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Quantization noice
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Digital transmission
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Distorsion
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Effect of attenuation, distortion, and noise on transmitted signal.
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Point-to-point communication
Mikrofon Högtalare
Source coding Source decodingDigitalizatingcompression
0110 0110
Error management Error control.
0100010
Bitfel
0110010
Flow control Flow control
Modulation Demodulation
0110010NACKACK
Layer6
Layer2
Layer1
Layer7
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Digital modulation methods
Binary signal
ASK = Amplitude Shift Keying (AM)
FSK = Frequency Shift Keying (FM)
PSK = Phase Shift Keying (PSK)
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0 0.005 0.01-2
0
2000
0 0.005 0.01-2
0
2001
0 0.005 0.01-2
0
2011
0 0.005 0.01-2
0
2010
0 0.005 0.01-2
0
2100
0 0.005 0.01-2
0
2101
0 0.005 0.01-2
0
2111
0 0.005 0.01-2
0
2110
8QAM example:Below you find eight symbols used for a so called 8QAM modem (QAM=Quadrature Amplitude Modulation). The symbols in the first row represent the messages 000, 001, 011 and 010 respectively (from left to right). The second row representents 100, 101, 111 and 110.
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a) The signal below is transmitted from the modulator. What bit sequency is transmitted?
0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04-2
0
2
Tid [sekunder]
Sp
än
nin
g [V
olt]
Modulatorns utsignal
b) The time axis is graded in seconds. What is the symbol rate in baud or symbols/s?
c) What is the bit rate in bit/s?
Example 2 cont.
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Bit rate vs baud rate
Bit rate in bit/s:
Where M is the number of symbols and fs is the symbol rate in baud or symbols/s.
2logb Sf f M
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Bit and baud rate comparison
ModulationModulation UnitsUnits BitsBits/symbol/symbol Baud rateBaud rate Bit Rate
ASK, FSK, 2-PSKASK, FSK, 2-PSK Bit 1 N N
4-PSK, 4-QAM4-PSK, 4-QAM Dibit 2 N 2N
8-PSK, 8-QAM8-PSK, 8-QAM Tribit 3 N 3N
16-QAM16-QAM Quadbit 4 N 4N
32-QAM32-QAM Pentabit 5 N 5N
64-QAM64-QAM Hexabit 6 N 6N
128-QAM128-QAM Septabit 7 N 7N
256-QAM256-QAM Octabit 8 N 8N
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Figure 5.14 The 4-QAM and 8-QAM constellations
Q (Quadrature phase)
I (Inphase)
Q (Quadrature phase)
I (Inphase)
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Sine wave example
I
5 Volt
л/2 radians = 90º
Complex representation
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Inphase and quadrature phase signal Sine wave as reference (inphase) signal:
Cosine wave as reference (inphase) signal:
( ) ( )sin(2 ) ( ) cos(2 ).c cs t I t f t Q t f t
( ) ( ) cos(2 ) ( )sin(2 ).c cu t I t f t Q t f t
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Complex baseband representation
C = I+jQ
Amplitude:
Phase:
RF signal (physical bandpass signal, if a cosine is reference signal):
2 2C I Q I
jQ
C|C|
Arg C
arctan , if 0arg( )
arctan , if 0
QI
II jQQ
II
( ) cos(2 arg ).cs t C f t C
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Equivalent baseband signal
( ) ( )sin(2 ) ( ) cos(2 ).c cs t I t f t jQ t f t
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Figure 5.11 The 4-PSK characteristics
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Figure 5.12 The 8-PSK characteristics
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Figure 5.16 16-QAM constellations
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Spectrum of ASK, PSK and QAM signal
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Figure 3.9 Three harmonics
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Figure 3.10 Adding first three harmonics
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Example: Square Wave
Square wave with frequency fo
Component 1:
Component 5:
Component 3:
.
.
.
.
.
.
...}5cos5
13cos
3
1{cos
4)( ttt
Ats ooo
tA
ts o
cos4
)(1
tA
ts o
3cos3
4)(3
tA
ts o
5cos5
4)(5
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Figure 3.11 Frequency spectrum comparison
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Filtering the Signal Filtering is equivalent to cutting all the frequiencies outside the band of the
filter
High pass
INPUTS1(f)
H(f)
H(f)
OUTPUT S2(f)= H(f)*S1(f)
Low pass
INPUTS1(f)
H(f)
H(f)
f
OUTPUT S2(f)= H(f)*S1(f)
Band pass
INPUTS1(f)
H(f)
H(f)
OUTPUT S2(f)= H(f)*S1(f)
• Types of filters– Low pass
– Band pass
– High pass
f
f
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Figure 6.4 FDM (Frequency division multiplex)
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Figure 6.5 FDM demultiplexing example
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Figure 6.19 Time division multiplex (TDM) in the american telephone network
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Multiple access = channel access Several transmitters sharing the same physical medium, for
example wireless network, bus network or bus network.Based on
A physical layer multiplexing scheme A data link layer MAC protocol (medium access control) that avoids
collisions, etc.
Examples: TDMA (time division multiple-access) based on TDM FDMA (time division multiple-access) based on FDM CDMA based on spread spectrum multiplexing CSMA (carrier sense multiple-access) based on packet switching =
statistical multiplexing
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Cellular telephony generations
1G: (E.g. NMT 1981) Analog, FDMA circuit switched.
2G: (E.g. GSM 1991) Digital, FDMA+TDMA, 8 timeslots, circuit switched.
2.5G: (GPRS) Packet switched = statistical multiplexing. The old circuit switched infrastructure is kept.
3G: (e.g. WCDMA) FDMA + CDMA (= spread spectrum).
4G: (E.g. 3gpp LTE) All-IP. OFDM or similar.
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Spread spectrum
DS-CDMA = Direct Sequence Code DivisionMultiple Access
Chip sequencies
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Figure 13.15 Encoding rules
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Figure 13.16 CDMA multiplexer
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Figure 13.17 CDMA demultiplexer
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Figure 9.1 Discrete Multi Tone (DMT)
Essentially the same thing as OFDMUsed in ADSL modems
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Figure 9.2 ADSL Bandwidth division
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0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2-1
0
1
Sub
carr
ier
1
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2-1
0
1
Sub
carr
ier
20 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
-1
0
1
Sub
carr
ier
3
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2-1
0
1
Sub
carr
ier
4
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2-5
0
5
Sum
sig
nal
Time [ms]
OFDM modulation
A simple example:4 sub-carriers
8 PSK
-1.5 -1 -0.5 0 0.5 1 1.5-1.5
-1
-0.5
0
0.5
1
1.5
000
001
010
011
100
101
110
111
The 8PSK constellation
cos
-sin
{ { { { { {30 k=1 k=31 k=4 k=2k=0
OFDM symbol 1 OFDM symbol 2
0 0 0 1 0 0 0 1 0 0 1 0 1 1 1 0 0 0 0 1 0 0 0 0kk k == =
< >E5F1442443144444444444444424444444444444443 14444444444444244444444444443
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Technical data for DAB and DVB-T DAB DVB-T
Adopted 1995 1997
Coverage in parts of: Canada, Europe, Australia Europe and Australia
Net bit rate R per frequency channel:
576 - 1152 kbit/s 4.98 - 31.67 Mbit/s
Channel separation B: 1.712 MHz 8 MHz
Link level spectrum efficiency R/B:
0.34 - 0.67 bit/s/Hz 0.62 - 4.0 bit/s/Hz
Freq. range of today’s receivers:
174 – 240 MHz , 1452 – 1492 MHz.
470 - 862 MHz
Maximum speed: About 200 - 600 km/h 36 - 163 km/h
Number of OFDM sub-carriers:
1536, 384, 192 or 768. The 2K mode: 1705 The 8K mode: 6817
Sub-carrier modulation: DQPSK QAM, 16QAM or 64QAM
Inner Forward Error Correction Coding (FEC):
Convolutional coding with code rates 1/4, 3/8 or 1/2.
Convolutional coding with code rates 1/2, 2/3, 3/4, 5/6 or 7/8.
Outer FEC: None RS(204,188,t=8)
Time (outer) interleaving: Convolutional interleaving of depth 384 ms.
Convolutional interleaving of depth 0.6 - 3.5 ms.
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Orthogonal Frequency Division Multiplex (OFDM)Summary of advantages Can easily adapt to severe channel conditions without complex equalization Robust against narrow-band co-channel interference Robust against Intersymbol interference (ISI) and fading caused by
multipath propagation High spectral efficiency Efficient implementation using FFT Low sensitivity to time synchronization errors Tuned sub-channel receiver filters are not required (unlike conventional
FDM) Facilitates Single Frequency Networks, i.e. transmitter macrodiversity.
Summary of disadvantages Sensitive to Doppler shift. Sensitive to frequency synchronization problems. Inefficient transmitter power consumption, due to linear power amplifier
requirement.
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Bit error rate (BER) = Bit error probability = Pb
Packet error rate (PER) = Packet error probability for packet length N bits:Pp = 1 – (1-Pb)N
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Error-correcting codes (ECC), also known as Forward-error correcting codes (FCC)
A block code converts a fixed length of K data bits to a fixed length N codeword, where N > K.
A convolutions code inserts redundant bits into the bit-stream. Code rate ¾ means that for every 3 information bit, totally 4 are transferred, i.e. every forth of the transferred bits is redundant.
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Bit rates
Gross bit rate = Transmission rate. Symbol rate = Baud rate ≤ Gross bit rate In spread spectrum: Chip rate ≥ Bit rate ≥
Symbol rate. In FEC: Net bit rate = Information rate =
Useful bit rate ≤ Code rate * Gross bit rate Maximum throughput ≤ Net bit rate Goodput ≤ Throughput
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Nyquist formula Gives the gross bit rate,without taking noise into
consideration: Symbol rate < Bandwidth*2 Bit rate < Bandwidth * 2log M
The above can be reached for line coding (base band transmission) and so called single-sideband modulation. Howeverm in practice most digital modulation methods give: Symbol rate = Bandwidth
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Signal to noise ratios S/N= SNR = Signal-to-noise ratio. Often same thing as
C/N=CNR = Carrier-to-noise ratio SNR in dB = 10 log10 (S/N)
S/I = SIR = Signal-to-interference ratio. Often the same thing as C/I=CIR = Carrier-to-interference ratio. I is the cross-talk power.
CINR = C/(I+N) = Carrier-to-noise and interference ratio Eb/N0 = Bit-energy (Power in watt divided by bitrate)
divided by Noise density (in Watt per Hertz) Es/N0 = Symbol-energy (Power in Watt divided by
bitrate) divided by Noise density (in Watt per Hertz)
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Shannon-Heartly formula
Gives the channel capacity, i.e. the maximum information rate (useful bit rate) excluding bit error rate.
I=B * 2log (1+C/N)
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Some statistical distributions
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Gaussian noise
Time
Voltage
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Gaussian = Normal distributionProbability density funciton
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Additive White Gaussian Noise (AWGN) channel White noise = wideband (unfiltered) noise
with constant noise density in Watt/Hertz Pink noise = lowpass-filtered noise. Additive = linear mixing.
+Signal
Noise source
Noisy signal
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Channel Noise
Info
Error Rate Calculation
Tx
Rx
Error Rate Calculation
BSC
Binary SymmetricChannel
BernoulliBinary
Bernoulli BinaryGenerator
0
Display
0 1 0 1 1 0 1 0 0 1 0
Bernoulli distribution
Random sequence of independent 0:s and 1:s.
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Exponential distribution
Commonly used for time between phone calls and length of phonecalls. Simple model for calcuclation and simulation, but does not reflect data traffic bursty nature.
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More commons distributions
Poisson distribution Rectangular distribution Discrete distributions, for example the
distribution of a dice