Assignment 1

Report
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.
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 Matlab
that allows graphical data-flow
oriented programming.
…and about Network Simulation using tools
such as Opnet, NS/2, etc
Aim of the course
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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,
SIMULINK and/or Opnet.
This may include modelling and simulation of traffic sources,
channel models, modulation schemes, error coding schemes,
equalizers, algorithms, protocols and network topologies.
A real-world project is studied within an application area such
as wireless sensor networks, cellular communications,
modems for broadband access, wireless networks, shortrange communication, digital TV transmission, IP-TV or IPtelephony.
Prerequisites
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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
Litterature

Matlab, Simulink and Opnet
documentation will be provided
electronically.
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Please repeat physical layer issues and
datalink layer issues in basic books in
Computer Networks and Wireless Internet
Access.
Requirements
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All lectures and supervision lessons are mandatory.
You should attend 80% of the mandatory lessons.
You are expected to devote 20 hours/week to this
course.
Quzzes (multiple choice tests): At least 70% correct
answers.
Lab: About 20 hours of work.
Homework problem.
Oral presentations.
Project
Requirements on the project
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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.
Grading is based on

Keeping deadlines.
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Quzzes.
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Showing good understanding when andwering questions
from teachers and other students about your
presentations.
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Extent of own code.
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Research relevance.
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Own new results or conclusions.
Assignment 1: Theory repetition

The first assignment consists of old exam problems in
Computer Networks A, Wireless Internet access B and
Telecommunications B.

Deadline: Friday course week 2. Be prepared to present
your answers on the whiteboard.
Assignment 2: Simulink lab
exercize
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Takes about 10-15 hours to do.
Deadline: Course week 3
Assignment 3: Present a standard and an existing
simulation model
Essentially chapter 2 (theory) and 3 (existing model that you start out from) of your report. Examples
1.
802.11b PHY Simulink model and adaptive modulation and link control
2.
256 channel ADSL and bit loading.
3.
Bluetooth Voice Transmission
4.
Bluetooth Full Duplex Voice and Data Transmission – Also describe Bluetooth low energy mode. Can be extended
to thesis project.
5.
Digital Video Broadcasting Model (DVB-T). Also describe DVB-T2.
6.
NFC (Simulink model by previous years students – see Mathworks file archive).
7.
IEEE 802.11a WLAN Physical Layer. Also describe newer standards. 802.11n, 802.11ac, ad or v positioning. Stefan, Erik,
Andreas Gabriel.
8.
CDMA2000 Physical Layer.
9.
WCDMA Coding and Multiplexing.
10.
WCDMA Spreading and Modulation
11.
WCDMA End-to-end Physical Layer. Hassan, Lamin.
12.
Ultrawideband (UWB/wireless USB). See mathworks file archive. Fredrik, Markus, Seb
13.
ZigBee Simulink or Prowler model and IEEE 802.15.4g (smart grid). See mathworks file central. Altahra.
14.
ZigBee Prowler model and Multihop routing protocols (Prowler model) . You may demonstrate simulink model (see
Matlab file central) or Prowler model. Perhaps you can add cooperative diversity. Yuxin Guo , Yu Tang, Suna Yin,
Mengjun Qin.
15.
Opnet Mac Protocol Mehrzad
16.
Mobile Wimax
17.
Long-term evolution (LTE) Phy Downlink with spatial modeling. Also describe LTE-A. cheng yang, shixian wen, wei liu
18.
Long-term evolution (LTE) and eMBMS
19.
Line codes. Comparison of RZ, NRZ, AMI, Manchester coding (used in 10 Mbps Ethernet), 4B5B (used in 100Base-TX Ethernet) and PAM5 (used in 1000Base-T
Gigabit Ethernet): For a code demonstrating RZ, NRZ, AMI and Manchester, see http://apachepersonal.miun.se/~rogols/teaching/mks/lab2/LineEncoding.mdl
This code also requires this MATLAB function: http://apachepersonal.miun.se/~rogols/teaching/mks/lab2/line_encoder.m . During the rest of the project you may further
develope the code to deal with 4B5B and PAM5, and to measure the bit error rate.
20.
21.
Acoustic modem (new model)
Acoustic QR code (continue on project by previous year’s students)
Assignment 3 (cont.)
Oral presentation: Course week 3. Talk 5-10 minutes per person.
Everyone should take notes, and everyone should ask questions and discuss the topic.
Present:
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A standard (mention things like radio frequency, bandwidth, bit rate, modulation, error control method, multiplex
method, multiple-access protocol, new/future versions)
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New versions of the standard or ongoing development
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Screen dumps – or demonstration of - an existing simulation
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Differences between simulation and full standard
For higher grades:
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Also cite a related research paper or a textbook, for example a simulation method with results. See
scholar.google.com or library.
Within one week after that: Submit report chapter 2 (theory/previous research) and chapter 3 (existing model)
Assignment 4: Quizzes
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Basic concepts, Matlab and Simulink concepts
Requirement: At least 70% correct answers.
You can do them over and over again until the deadline.
Assignment 5: Opnet lab
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Zigbee and multihop simulation in Opnet.
Takes about 4 hours to do.
Assignment 6: Present project
suggestion
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Oral presentation course week 6.
Present
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Problem formulation (chapter 1) – what to parameters to evaluate
Cite simulation done in a research paper (if you have not done so)
Planned own modification or development of model (chapter 4)
Submit or show report chapters 1 and 4 before christmas.
Assignment 7: Final project
presentation
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Demonstrate simulation code to teacher (and also in report appendice)
Oral presentation in mid-January of
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Results (chapter 5): Plot performance for several cases.
Conclusions (chapter 6). Discuss similarities and differences from result in a
cited research paper.
Provide a preliminary report when you give your oral presentation.
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.
19
This is how MATLAB looks like
Workspace
Command
history
Command window
20
More MATLAB windows
Figure window
Array editor
M-file editor
21
How to get help in MATLAB?
help functionsname
Shows unformatted text
doc funktionsnamn
Shows HTML documentation
in a browser
22
SIMULINK
SIMULINK: Toolbox in Matlab
that allows graphical data-flow
oriented programming.
Repetition of some basic concepts
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Frequency spectrum
Digitalisation, source coding
Error coding
Modulation
Multiple-access methods
Base-band model
Distorsion, noise
Signal-to-noise ratio
Bit-error ratio
Statistics
Repetition of some
basic concepts
Digitalization
PCM = Pulse Code Modulation =
Digital transmission of analogue signals
Number exemples from PSTN = the public telephone network
011011010001...
1
0
Anti aliasingfilter
Sampler
AD-converter
with
seerial output
DAconverter
Interpolation
filter
Loudspeaker
Microphone
8000
300-3400Hz
sampels
band pass
filter. Stops per sec
everything
over 4000Hz.
8 bit per sampel
i.e. 64000 bps
per phone call
28 = 256
voltage levels
Aliasing
Quantization noice
Digital transmission
Distorsion
Effect of attenuation, distortion,
and noise on transmitted signal.
Point-to-point communication
Layer
7
Layer
6
Mikrofon
Högtalare
Source coding
Digitalizating
compression
0110
Error management
Layer
2
NACK
ACK
0110010
Source decoding
0110
.
Error control
0100010
0110010
Bitfel
Layer
1
Flow control
Flow control
Modulation
Demodulation
Digital modulation methods
Binary signal
ASK = Amplitude
Shift Keying (AM)
FSK = Frequency
Shift Keying (FM)
PSK = Phase Shift
Keying (PSK)
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.
000
001
011
010
2
2
2
2
0
0
0
0
-2
0
0.005
100
-2
0.01 0
0.005
101
-2
0.01 0
0.005
111
-2
0.01 0
2
2
2
2
0
0
0
0
-2
0
0.005
-2
0.01 0
0.005
-2
0.01 0
0.005
-2
0.01 0
0.005
110
0.01
0.005
0.01
Example 2 cont.
a) The signal below is transmitted from the modulator. What bit
sequency is transmitted?
Spänning [Volt]
Modulatorns utsignal
2
0
-2
0
0.005
0.01
0.015 0.02 0.025
Tid [sekunder]
0.03
0.035
0.04
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?
Bit rate vs baud rate
Bit rate in bit/s:
fb  f S log 2 M
Where M is the number of symbols and fs
is the symbol rate in baud or symbols/s.
Bit and baud rate comparison
Units
Bits
/symbol
Baud rate
Bit Rate
Bit
1
N
N
4-PSK, 4-QAM
Dibit
2
N
2N
8-PSK, 8-QAM
Tribit
3
N
3N
16-QAM
Quadbit
4
N
4N
32-QAM
Pentabit
5
N
5N
64-QAM
Hexabit
6
N
6N
128-QAM
Septabit
7
N
7N
256-QAM
Octabit
8
N
8N
Modulation
ASK, FSK, 2-PSK
Figure 5.14
The 4-QAM and 8-QAM constellations
Q (Quadrature phase)
Q (Quadrature phase)
I (Inphase)
I (Inphase)
Sine wave example
Complex representation
5 Volt
л/2 radians =I 90º
Inphase and quadrature phase
signal

Sine wave as reference (inphase) signal:
s(t )  I (t )sin(2 fct )  Q(t )cos(2 fct ).

Cosine wave as reference (inphase) signal:
u(t )  I (t )cos(2 fct )  Q(t )sin(2 f ct ).
Complex baseband representation
jQ
C = I+jQ
Amplitude:
C  I Q
2
|C|
2
C
Arg C
Phase:
Q

if I  0
 arctan I ,
arg( I  jQ)  
arctan Q   , if I  0

I
RF signal (physical bandpass signal, if a cosine is
reference signal):
s(t )  C cos(2 fct  arg C).
I
Equivalent baseband signal
s(t )  I (t )sin(2 fct )  jQ(t )cos(2 fct ).
Figure 5.11 The 4-PSK characteristics
Figure 5.12
The 8-PSK characteristics
Figure 5.16
16-QAM constellations
Spectrum of ASK, PSK and QAM signal
Figure 3.9
Three harmonics
Figure 3.10
Adding first three harmonics
Example: Square Wave
Square wave with frequency fo
4A
1
1
s(t ) 
{cos ot  cos 3ot  cos 5ot  ...}

3
5
Component 1:
Component 3:
.
.
.
Component 5:
.
.
.
s1 (t ) 
4A
cos o t

4A
s3 (t ) 
cos 3ot
3
4A
s5 (t ) 
cos 5o t
5
Figure 3.11 Frequency spectrum comparison
Filtering the Signal

Filtering is equivalent to cutting all the frequiencies outside the band of the
filter
• Types of
filters
– Low pass
Low pass
H(f)
INPUT
S1(f)
OUTPUT
S2(f)= H(f)*S1(f)
H(f)
f
Band pass
– Band pass
H(f)
INPUT
S1(f)
OUTPUT
S2(f)= H(f)*S1(f)
H(f)
f
– High pass
High pass
H(f)
INPUT
S1(f)
H(f)
f
OUTPUT
S2(f)= H(f)*S1(f)
Figure 6.4
FDM (Frequency division multiplex)
Figure 6.5
FDM demultiplexing example
Figure 6.19
Time division multiplex (TDM) in the american telephone network
Multi-path propagation
Multiple access = channel access
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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 (frequency division multiple-access) based on FDM
CDMA based on spread spectrum multiplexing
CSMA (carrier sense multiple-access) based on packet switching =
statistical multiplexing
OFDMA
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.
Spread spectrum
DS-CDMA = Direct Sequence Code Division
Multiple Access
Chip sequencies
Figure 13.15
Encoding rules
Figure 13.16
CDMA multiplexer
Figure 13.17
CDMA demultiplexer
Figure 9.1
Discrete Multi Tone (DMT)
Essentially the same thing as OFDM
Used in ADSL modems
Figure 9.2
ADSL Bandwidth division
The 8PSK constellation
011
001
-sin
0.5
0
100
000
-0.5
101
-1
-1.5
-1.5
111
110
-1
-0.5
0
cos
0.5
1
A simple example:
4 sub-carriers
8 PSK
1.5
Subcarrier 1
Subcarrier 4
010
Sum signal
1
Subcarrier 3
1.5
Subcarrier 2
OFDM
modulation
1
0
-1
1
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0
0.2
0.4
0.6
0.8
1
1.2
Time [ms]
1.4
1.6
1.8
2
0
-1
1
0
-1
1
0
-1
5
0
-5
000 100 010 010
111 000 010 000
Technical data for DAB and DVB-T
Adopted
Coverage in parts of:
Net bit rate R per
frequency channel:
Channel separation B:
Link level spectrum
efficiency R/B:
Freq. range of today’s
receivers:
Maximum speed:
Number of OFDM
sub-carriers:
Sub-carrier modulation:
Inner Forward Error
Correction Coding (FEC):
Outer FEC:
Time (outer) interleaving:
DAB
DVB-T
1995
Canada, Europe, Australia
576 - 1152 kbit/s
1997
Europe and Australia
4.98 - 31.67 Mbit/s
1.712 MHz
0.34 - 0.67 bit/s/Hz
8 MHz
0.62 - 4.0 bit/s/Hz
174 – 240 MHz ,
1452 – 1492 MHz.
About 200 - 600 km/h
1536, 384, 192 or 768.
470 - 862 MHz
DQPSK
Convolutional coding with
code rates 1/4, 3/8 or 1/2.
None
Convolutional interleaving
of depth 384 ms.
36 - 163 km/h
The 2K mode: 1705 The 8K
mode: 6817
QAM, 16QAM or 64QAM
Convolutional coding with code
rates 1/2, 2/3, 3/4, 5/6 or 7/8.
RS(204,188,t=8)
Convolutional interleaving of
depth 0.6 - 3.5 ms.
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.
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
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.

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

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 singlesideband modulation. Howeverm in practice
most digital modulation methods give:
 Symbol
rate = Bandwidth
Signal to noise ratios

S/N= SNR = Signal-to-noise ratio. Often same thing as
C/N=CNR = Carrier-to-noise ratio
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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)
Shannon-Heartly formula

Gives the channel capacity, i.e. the
maximum information rate (useful bit rate)
excluding bit error rate.
I=B log2 (1+C/N)
Where C/N is carrier-to-noise ratio (sometimes
called S/N)
Some statistical
distributions
Gaussian noise
Voltage
Time
Gaussian = Normal distribution
Probability density funciton
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
Noisy signal
+
Noise source
Bernoulli distribution
Channel Noise
0
Tx
0 1 0 1BSC
1010010
Bernoulli
Binary
Error Rate
Rx Calculation
Error Rate Calculation
Bernoulli Binary
Generator
Binary Symmetric
Channel
Info
Random sequence of independent 0:s and 1:s.
Display
Exponential distribution
Commonly used for time between phone calls and length of phone
calls. Simple model for calculation and simulation,
but does not reflect data traffic bursty nature.
Multi-path propagation
Rayleigh distribution

Model of rayleigh fading, i.e. amplitude
gain caused by multi-path propagation
with no line-of-sight
More commons distributions
Ricean distribution (fading with line-ofsight)
 Poisson distribution (number of phone
calls during a phone call)
 Self-similar process (bursty data traffic)
 Rectangular distribution
 Discrete distributions, for example the
distribution of a dice


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