simulating communication systems with matlab: an introduction
DESCRIPTION
Download related MATLAB codes from http://www.freewebs.com/acwebpage/Resources/Codes_Comm_PPT.zipTRANSCRIPT
September 23, 2010
NIT DGP Student Branch
Aniruddha ChandraECE Department, NIT Durgapur, WB, India.
Simulating Communication Systems Simulating Communication Systems with MATLAB : An Introductionwith MATLAB : An Introduction
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 2
Sep. 23, 2010Presentation OutlinePresentation Outline
Objective of the Lecture
Expected Background
Simulating Analog Communication Systems Amplitude Modulation (AM)
Simulating Digital Communication SystemsBinary Phase Shift Keying (BPSK)
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 3
Sep. 23, 2010Presentation OutlinePresentation Outline
Objective of the Lecture
Expected Background
Simulating Analog Communication Systems Amplitude Modulation (AM)
Simulating Digital Communication SystemsBinary Phase Shift Keying (BPSK)
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 4
Sep. 23, 2010Objective of the LectureObjective of the Lecture
After the Lecture … You’ll be able to
Write your own Matlab Script
Make a Analog/ Digital Communication Link
Compare your Results with Theoretical Values
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 5
Sep. 23, 2010Presentation OutlinePresentation Outline
Objective of the Lecture
Expected Background
Simulating Analog Communication Systems Amplitude Modulation (AM)
Simulating Digital Communication SystemsBinary Phase Shift Keying (BPSK)
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 6
Sep. 23, 2010Expected BackgroundExpected Background
I assume that …You understand
Basic MATLAB Operations (function, matrix)
Basics of Communication (modulation)
Performance Metrics (BER)
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 7
Sep. 23, 2010Presentation OutlinePresentation Outline
Objective of the Lecture
Expected Background
Simulating Analog Communication Systems Amplitude Modulation (AM)
Simulating Digital Communication SystemsBinary Phase Shift Keying (BPSK)
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 8
Sep. 23, 2010Analog Communication SystemsAnalog Communication Systems
Source
Channel
Destination Demodulator
Modulator
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 9
Sep. 23, 2010Simulate a SourceSimulate a Source
Source
Channel
Destination Demodulator
Modulator
Produces message signal … e.g. a simple Sine wave
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 10
Sep. 23, 2010
Generate message signal (simple sine wave)
Define time instants (1000 sample points)tmin = 0; tmax = 10^(-3); step = (tmax-tmin)/1000;t = tmin:step:tmax;
Define amplitude and frequency (initial phase is zero)Vm = 1; % Amplitudefm = 2*10^3; % Frequency
Construct the Signalm = Vm*sin(2*pi*fm*t);
View the Signalplot(t,m,'r');
Simulate a SourceSimulate a Source
tfVtm mm 2sin
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 11
Sep. 23, 2010
Complete MATLAB Script [Prog1.m]
tmin = 0; tmax = 10^(-3); step = (tmax-tmin)/1000;t = tmin:step:tmax; fm = 2*10^3; Vm = 1; m = Vm*sin(2*pi*fm*t); plot(t,m,'r');
Simulate a SourceSimulate a Source
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 12
Sep. 23, 2010Simulate a SourceSimulate a Source
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 13
Sep. 23, 2010Simulate a SourceSimulate a Source
Assignment #1 [Prog2.m], [Prog3.m]
What happens if there is an initial phase?phi_deg = 45;phi_rad = phi_deg*pi/180;m = Vm*sin(2*pi*fm*t+phi_rad);
What happens if the message is not sinusoidal?tmin = 0; tmax = 1; step = (tmax-tmin)/1000;t = tmin:step:tmax;f = 2; m = sawtooth(2*pi*f*t);plot(t,m,'r');
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 14
Sep. 23, 2010Simulate ModulationSimulate Modulation
Source
Channel
Destination Demodulator
Modulator
Built-in functions are available (ammod, amdemod etc.)
WYSIWYG?? No
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 15
Sep. 23, 2010Amplitude ModulationAmplitude Modulation
Simulate with built-in functions [Prog4.m]
fs = 8000; % Sampling rate is 8000 samples per secondfc = 300; % Carrier frequency in Hzt = [0:0.1*fs]'/fs; % Sampling times for 0.1 secondm = sin(20*pi*t); % Representation of the signalv = ammod(m,fc,fs); % Modulate m to produce v
figure(1)subplot(2,1,1); plot(t,m); % Plot m on topsubplot(2,1,2); plot(t,v); % Plot v below
mr = amdemod(v,fc,fs); % Demodulate v to produce m
figure(2);subplot(2,1,1); plot(t,m); % Plot m on topsubplot(2,1,2); plot(t,mr); % Plot mr below
Source: Introduction to Communications Toolbox in MATLAB 7.6.0 (R2008) by Amit DegadaAvailable: http://amitdegada.weebly.com/download.html
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 16
Sep. 23, 2010Amplitude ModulationAmplitude Modulation
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 17
Sep. 23, 2010Amplitude ModulationAmplitude Modulation
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 18
Sep. 23, 2010Amplitude ModulationAmplitude Modulation
Don’t have the feel??? …. Try this
Define message signal, (as done earlier)
tmin = 0; tmax = 10^(-3); step = (tmax-tmin)/1000;t = tmin:step:tmax;Vm = 1;fm = 2*10^3;m = Vm*sin(2*pi*fm*t);
Define carrier,
Vc = 2; % Amplitudefc = 10^4; % Frequencyc = Vc*sin(2*pi*fc*t); % Carrier signal
tfVtm mm 2sin
tfVtc cc 2sin
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 19
Sep. 23, 2010Amplitude ModulationAmplitude Modulation
Continued ….
Modulate the Signal,
v = (1+m/Vc).*c; % DSB-FC modulation
View Modulated Wave
plot(t,v); % Modulated Wavehold on; plot(t,Vc*(1+m/Vc),'r:'); % Upper Envelopehold on; plot(t,-Vc*(1+m/Vc),'r:'); % Lower Envelopehold off ;
tftfV
VVtv cm
c
mc
2sin2sin1
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 20
Sep. 23, 2010
Complete MATLAB Script [Prog5.m]
clear all; close all; clc;tmin = 0; tmax = 10^(-3); step = (tmax-tmin)/1000;t = tmin:step:tmax; % TimeVm = 1; Vc = 2; % Amplitude fm = 2*10^3; fc = 10^4; % Frequency
m = Vm*sin(2*pi*fm*t); % Messagec = Vc*sin(2*pi*fc*t); % Carrierv = (1+m/Vc).*c; % Modulated Wave
plot(t,v); hold on; plot(t,Vc*(1+m/Vc),'r:'); hold on; % Upper Envelopeplot(t,-Vc*(1+m/Vc),'r:'); hold off % Lower Envelope
Amplitude ModulationAmplitude Modulation
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 21
Sep. 23, 2010Amplitude ModulationAmplitude Modulation
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 22
Sep. 23, 2010
Assignment #2 [Prog6.m]
How to view effect of changing modulation index? tmin = 0; tmax = 10^(-3); step = (tmax-tmin)/1000;t = tmin:step:tmax; Vm = 1; mu = 1.5; Vc = Vm/mu; fm = 2*10^3; fc = 10^4;
m = Vm*sin(2*pi*fm*t); c = Vc*sin(2*pi*fc*t); v = (1+m/Vc).*c;
plot(t,v); hold on; plot(t,Vc*(1+m/Vc),'r:'); hold on; plot(t,-Vc*(1+m/Vc),'r:'); hold off
Amplitude ModulationAmplitude Modulation
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 23
Sep. 23, 2010
Assignment #2 (Contd…) [Prog7.m]
How to simulate DSB-SC modulation?tmin = 0; tmax = 10^(-3); step = (tmax-tmin)/1000;t = tmin:step:tmax; Vm = 2; Vc = 1; fm = 2*10^3; fc = 10^4;
m = Vm*sin(2*pi*fm*t); c = Vc*sin(2*pi*fc*t); v = m.*c;
plot(t,v); hold on; plot(t,m,'r:'); hold on; plot(t,-m,'r:'); hold off
Amplitude ModulationAmplitude Modulation
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 24
Sep. 23, 2010DemodulationDemodulation
Demodulate DSB-SC with filter [Prog8.m]
clear all; close all; clc;tmin = 0; tmax = 1; step = (tmax-tmin)/(10^3);t = tmin:step:tmax; Vm = 2; Vc = 1; fm = 2; fc = 10^2;
m = Vm*sin(2*pi*fm*t); c = Vc*sin(2*pi*fc*t); v = m.*c;
r = v.*c;
[b a] = butter(1,0.01);mr = filter(b,a,r);
figure(1)subplot(2,1,1); plot(t,m);subplot(2,1,2); plot(t,mr);
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 25
Sep. 23, 2010DemodulationDemodulation
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 26
Sep. 23, 2010
Ideal Demodulation of DSB-SC [Prog9.m]
clear all; close all; clc;fs = 10^5; N = 10^5; t = 1/fs:1/fs:N/fs; fm = 2; fc = 10^3; m = sin(2*pi*fm*t); c = sin(2*pi*fc*t); v = m.*c;
r = zeros(1,N); n =f s/fc;for k = 1:fc mr((k-1)*n+1:k*n) = 2*v((k-1)*n+1:k*n)*c((k-1)*n+1:k*n)'/n;end
figure(1)subplot(2,1,1); plot(t,m);subplot(2,1,2); plot(t,mr);
DemodulationDemodulation
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 27
Sep. 23, 2010DemodulationDemodulation
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 28
Sep. 23, 2010Analog Communication SystemsAnalog Communication Systems
Source
Channel
Destination Demodulator
Modulator
Introduces noise … Additive White Gaussian Noise
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 29
Sep. 23, 2010Simulate ChannelSimulate Channel
Introducing AWGN [Prog10.m]
fs = 10^5; N = 10^5; t = 1/fs:1/fs:N/fs; fm = 2; fc = 10^3; m = sin(2*pi*fm*t); c = sin(2*pi*fc*t); v = m.*c;
SNRdB = 10; SNR = 10^(SNRdB/10);vn = var(v)/SNR;n = sqrt(vn)*randn(1,N);v = v + n;
r=zeros(1,N); n=fs/fc;for k=1:fc mr((k-1)*n+1:k*n)=2*v((k-1)*n+1:k*n)*c((k-1)*n+1:k*n)'/n;end
figure(1)subplot(2,1,1); plot(t,m);subplot(2,1,2); plot(t,mr); axis([0 1 -1 1])
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 30
Sep. 23, 2010Simulate ChannelSimulate Channel
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 31
Sep. 23, 2010Presentation OutlinePresentation Outline
Objective of the Lecture
Expected Background
Simulating Analog Communication Systems Amplitude Modulation (AM)
Simulating Digital Communication SystemsBinary Phase Shift Keying (BPSK)
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 32
Sep. 23, 2010Digital Communication SystemsDigital Communication Systems
Source
Channel
Destination Demodulator
Modulator
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 33
Sep. 23, 2010Simulate BPSKSimulate BPSK
Simulation [Prog11.m]
%This program simulates BER of BPSK in AWGN channel% clear all; close all; clc; num_bit=100000; %Signal length max_run=20; %Maximum number of iterations for a single SNR Eb=1; %Bit energy SNRdB=0:1:9; %Signal to Noise Ratio (in dB) SNR=10.^(SNRdB/10);
hand=waitbar(0,'Please Wait....'); for count=1:length(SNR) %Beginning of loop for different SNR avgError=0; No=Eb/SNR(count); %Calculate noise power from SNR
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 34
Sep. 23, 2010Simulate BPSKSimulate BPSK
Simulation (Contd.) [Prog11.m] for run_time=1:max_run %Beginning of loop for different runs waitbar((((count-1)*max_run)+run_time-1)/(length(SNRdB)*max_run)); Error=0; data=randint(1,num_bit); %Generate binary data source s=2*data-1; %Baseband BPSK modulation N=sqrt(No/2)*randn(1,num_bit); %Generate AWGN Y=s+N; %Received Signal for k=1:num_bit %Decision device taking hard decision and deciding error if ((Y(k)>0 && data(k)==0)||(Y(k)<0 && data(k)==1)) Error=Error+1; end end Error=Error/num_bit; %Calculate error/bit avgError=avgError+Error; %Calculate error/bit for different runs end %Termination of loop for different runs
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 35
Sep. 23, 2010Simulate BPSKSimulate BPSK
Simulation (Contd.) [Prog11.m]
BER_sim(count)=avgError/max_run; %Calculate BER for a particular SNR end %Termination of loop for different SNR BER_th=(1/2)*erfc(sqrt(SNR)); %Calculate analytical BER close(hand); semilogy(SNRdB,BER_th,'k'); %Plot BER hold on semilogy(SNRdB,BER_sim,'k*'); legend('Theoretical','Simulation',3); axis([min(SNRdB) max(SNRdB) 10^(-5) 1]); hold off
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 36
Sep. 23, 2010Simulate BPSKSimulate BPSK
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 37
Sep. 23, 2010ReferencesReferences
[1] http://www.mathworks.com/matlabcentral/
[2] http://www.freewebs.com/acwebpage/teaching.htm
[3] B.P. Lathi and Z. Ding, Modern Digital and Analog Communication Systems, Oxford University Press, International 4th edition, 2010.
[4] J.G. Proakis, M. Salehi, and G. Bauch, Contemporary Communication Systems using MATLAB, Thomson/ CL-Engineering, 2nd edition, 2003.
A. Chandra, ECE Deptt., NITD Simulating Communication Systems with MATLAB 38
Sep. 23, 2010
Thank You!