Digital Communication Projects using Matlab.
1. Multiple Input Multiple Output(MIMO) using Matlab
clc;
close all;
clear all;
mT = 2; % No.of transmitters
mR = 2; % No.of receivers
ITER = 1000; % number of iterations.
SNRdB = [0:25]; % SNR maximum scale
SNR = 10.^(SNRdB/10); % SNR in decibels
C_SISO = zeros(1,length(SNR));
C_SIMO = zeros(1,length(SNR));
C_MISO = zeros(1,length(SNR));
C_MIMO = zeros(1,length(SNR));
for ite = 1:ITER
h_SISO = (randn +1i*randn)/sqrt(2);
h_SIMO = (randn(mR,1)+1i*randn(mR,1))/sqrt(2);
h_MISO = (randn(1,mT)+1i*randn(1,mT))/sqrt(2);
h_MIMO = (randn(mR,mT)+1i*randn(mR,mT))/sqrt(2);
for K = 1:length(SNR)
C_SISO(K) = C_SISO(K) + log2(1+ SNR(K)*norm(h_SISO)^2);
C_SIMO(K) = C_SIMO(K) + log2(1+ SNR(K)*norm(h_SIMO)^2);
C_MISO(K) = C_MISO(K) + log2(1+ SNR(K)*norm(h_MISO)^2/mT);
C_MIMO(K) = C_MIMO(K) + log2(abs(det(eye(mR)+SNR(K)*h_MIMO*h_MIMO'/mT)));
end
end
C_SISO = C_SISO/ITER;
C_SIMO = C_SIMO/ITER;
C_MISO = C_MISO/ITER;
C_MIMO = C_MIMO/ITER;
plot(SNRdB,C_SISO,'r',SNRdB,C_SIMO,'b',SNRdB,C_MISO,'m',SNRdB,C_MIMO,'k')
%legend('SISO','SIMO','MISO','MIMO')
xlabel('SNR in dB')
ylabel('Capacity (b/s/Hz)')
title('Capacity Vs. SNR')
grid;Output
2. Pulse Width Modulation(PWM) working Principal using Matlab
clc;
clear all;
close all;
F2=input('Messsage frequency=');
F1=input('Carrie Sawtooth Frequency=');
A=5;
t=0:0.001:1;
c=A.*sawtooth(2*pi*F1*t);
subplot(3,1,1)
plot(t,c);
xlabel('time')
ylabel('Amplitude');
title('Carrier Sawtooth Wave');
grid on;
m=0.75*A.*sin(2*pi*F2*t);
subplot(3,1,2);
plot(t,m);
xlabel('Time');
ylabel('Amplitude');
title('Message Signal');
grid on;
n=length(c);
for i=1:n
if (m(i)>=c(i))
pwm(i)=1;
else
pwm(i)=0;
end
end
subplot(3,1,3);
plot(t,pwm);
xlabel('Time');
ylabel('Amplitude');
title('plot of PWM');
axis([0 1 0 2]);
grid on;Output
3. Quadrature Amplitude Modulation(QAM)
Fd=1;Fs=1;
nsamp=1;
M=32;
k = log2(M);
n = 30000;
x = randi([0 1],n,1);
stem(x(1:40),'filled');
title('Random Bits');
xlabel('Bit Index');
ylabel('Binary Value');
xsym = bi2de(reshape(x,k,length(x)/k).');
figure;
stem(xsym(1:10));
title('Random Symbols');
xlabel('Symbol Index');
ylabel('Integer Value');
y=qammod(xsym,M);
title('modulated');
xlabel('Symbol Index');
ylabel('Integer Value');
ytx = y;
stem(y(1:10));
EbNo=10;
snr = EbNo + 10*log10(k) - 10*log10(nsamp);
pinput=std(ytx);
noise = (randn(1,n/k)+sqrt(-1)*randn(1,n/k))*(1/sqrt(2));
Noisestd = (pinput*10^(-snr/20));
ynoisy = ytx + (Noisestd*noise);
yrx=ynoisy;
figure;
plot(real(yrx(1:5e3)),imag(yrx(1:5e3)),'b*');
hold on;
plot(real(ytx(1:5e3)),imag(ytx(1:5e3)),'y.');
title('Signal Constellation');
legend('Received Signal', 'Transmitted Signal');
axis([-5 5 -5 5]);
hold off;Output
4. MATLAB code for Binary Frequency Shift Keying(BFSK) Modulation and Demodulation
clc;
clear all;
N=8;
b=round(rand(1,N));
subplot(4,1,1);
stem(b,'filled')
xlabel('Bits index')
ylabel('transmitted bits')
NRZ_out=[];
Vp=1;
for index=1:size(b,2)
if b(index)==1
NRZ_out=[NRZ_out ones(1,200)*Vp];
elseif b(index)==0
NRZ_out=[NRZ_out zeros(1,200)*(-Vp)];
end
end
subplot(4,1,2);
plot(NRZ_out)
t=0.005:0.005:8;
f2=3;
f1=5;
A=5;
mod_sig=[];
for(i=1:1:length(NRZ_out))
if(NRZ_out(i)==1)
y=A*cos(2*pi*f1*t(i));
else
y=A*cos(2*pi*f2*t(i));
end
mod_sig=[mod_sig y];
end
subplot(4,1,3);
plot(t,mod_sig)
xlabel('Time in seconds')
ylabel('Modulated signal')
demod_branch_1=mod_sig.*(cos(2*pi*f1*t));
demod_branch_2=mod_sig.*(cos(2*pi*f2*t));
y_1=[];
for i=1:200:size(demod_branch_1,2)
y_1=[y_1 trapz(t(i:i+199),demod_branch_1(i:i+199))];
end
y_2=[];
for i=1:200:size(demod_branch_2,2)
y_2=[y_2 trapz(t(i:i+199),demod_branch_2(i:i+199))];
end
rec_sig=y_1>y_2;
subplot(4,1,4);
stem(rec_sig,'filled','r')
xlabel('Bits index')
ylabel('Received bits')Output
5. Pulse Code Modulation (PCM)
P=5;
t = [0:0.1:1*pi];
sig = 4*sin(t);
Vh=max(sig);
V1=min(sig);
N=3;M=2^N;
S=(Vh-V1)/M;
partition = [V1+S:S:Vh-S];
codebook = [V1+S/2:S:Vh-S/2];
[index,quantized_sig,distor] = quantiz(sig,partition,codebook);
codedsig=de2bi(index,'left-msb');
codedsig=codedsig;
txbits=codedsig(:);
errvec=randsrc(length(txbits),1,[0 1;(1-P/100) P/100]);
rxbits=rem(txbits+errvec,2);
rxbits=reshape(rxbits,N,length(sig));
rxbits=rxbits';
index1=bi2de(rxbits,'left-msb');
reconstructedsig=codebook(index1+1);
figure,
subplot(2,2,1);
stem(t,sig);
xlabel('Time');
title('original signal');
subplot(2,2,2);
stem(t,quantized_sig);
xlabel('time)');
title('quantized signal');
tt=[0:N*length(t)-1];
subplot(2,2,3);
stairs(tt,txbits);
xlabel('time');
title('PCM Waveform');
subplot(2,2,4);
stem(t,reconstructedsig);
xlabel('time');
title('received signal');
6. Quadrature Phase Shift Keying (QPSK), Matlab Code
clc;
clear al;
close all;
Tb=1;
t=0:(Tb/100):Tb;
fc=1;
c1=sqrt(2/Tb)*cos(2*pi*fc*t);
c2=sqrt(2/Tb)*sin(2*pi*fc*t);
subplot(3,2,1);
plot(t,c1);
title('Carrier Signal-1');
xlabel('t ----->');
ylabel('c1(t)');
grid on;
subplot(3,2,2);
plot(t,c2);
title('Carrier Signal-2');
xlabel('t ----->');
ylabel('c2(t)');
grid on;
N=16;
m=rand(1,N);
t1=0;
t2=Tb;
for i=1:2:(N-1)
t=[t1:(Tb/100):t2];
if m(i)>0.5
m(i)=1;
m_s=ones(1,length(t));
else
m(i)=0;
m_s=-1*ones(1,length(t));
end
odd_sig(i,:)=c1.*m_s;
if m(i+1)>0.5
m(i+1)=1;
m_s=ones(1,length(t));
else
m(i+1)=0;
m_s=-1*ones(1,length(t));
end
even_sig(i,:)=c2.*m_s;
Qpsk =odd_sig + even_sig;
subplot(3,2,3);
stem(m);
title('Binary Data of Message Signal');
xlabel('n ----->');
ylabel('b(n)');
grid on;
subplot(3,2,4);
plot(t,Qpsk(i,:));
title('QPSK Modulated Signal');
xlabel('t ------>');
ylabel('s(t)');
grid on;
hold on;
t1=t1+(Tb+0.01);
t2=t2+(Tb+0.01);
end
hold off;
t1=0;
t2=Tb;
for i=1:N-1
t=[t1:(Tb/100):t2];
x1=sum(c1.*Qpsk(i,:));
x2=sum(c2.*Qpsk(i,:));
if (x1>0 && x2>0)
demod(i)=1;
demod(i+1)=1;
elseif (x1>0 && x2<0)
demod(i)=1;
demod(i+1)=0;
elseif (x1<0 && x2<0)
demod(i)=0;
demod(i+1)=0;
elseif (x1<0 && x2>0)
demod(i)=0;
demod(i+1)=1;
end
end
subplot(3,2,5);
stem(demod);
title('QPSK Demodulated Signal');
xlabel('n ------>');
ylabel('b(n)');
grid on;Output
7. Differential Phase Shift Keying (DPSK), Matlab code
clc;
clear al;
close all;
N=10;
bk=round(rand(1,N));
br=10^6;
f=br;
T=1/br;
grid on;
subplot(4,1,1);
stem(bk,'linewidth',1.5);
title('INFORMATION BITS TO BE TRANSMITTED');
axis([0 11 0 1.5]);
dk=1;
coded =[dk];
for i=1:length(bk)
temp=~xor(dk,bk(i));
coded=[coded temp];
dk=temp;
end
subplot(4,1,2);
stem(coded,'linewidth',1.5);
grid on;
title('Differentially encoded signal');
axis([0 11 0 1.5]);
coded_PNRZ=2*coded-1;
mod_sig=[];
t=T/99:T/99:T;
for i=1:length(coded)
temp=coded_PNRZ(i)*sqrt(2/T)*cos(2*pi*f*t);
mod_sig=[mod_sig temp];
end
subplot(4,1,3);
tt=T/99:T/99:(T*length(coded));
plot(tt,mod_sig,'linewidth',1.5);
title('dpsk modulation signal');
grid on;
rec_sig=mod_sig;
rec_data=[];
for i=1:length(coded)-1
y_in=rec_sig((i-1)*length(t)+1:i*length(t)).*rec_sig((i)*length(t)+1:(i+1)*length(t));
y_in_intg=trapz(t,y_in);
if (y_in_intg>0)
temp=1;
else
temp=0;
end
rec_data=[rec_data temp];
end
subplot(4,1,4);
stem(rec_data,'linewidth',3);
title('received information bits');
axis([0 11 0 1.5]);
8. BPSK(Binary Phase Shift Keying) Matlab Project code
clc;
clear all;
close all;
%fine Transmitted Signal=
N=10;
x_inp=round(rand(1,N)); % Message Signal
Tb=0.0001; % Bit Period
%Represent Input Signal as Digital Signal
x_bit=[];
nb=100;
for n=1:1:N
if x_inp(n)==1
x_bitt=ones(1,nb);
else
x_bitt=zeros(1,nb);
end
x_bit=[x_bit x_bitt];
end
t1=Tb/nb:Tb/nb:nb*N*(Tb/nb);
f1=figure(1);
set(f1,'color',[1 1 1]);
subplot(3,1,1);
plot(t1,x_bit,'LineWidth',2);
grid on;
axis([0 Tb*N -0.5 1.5]);
ylabel('Amplitude(volt)');
xlabel('Time(sec)');
title('Input Signal as Digital Signal');
%fine BPSK Modulation
Ac=10;
mc=4;
fc=mc*(1/Tb);
fi1=0;
fi2=pi;
t2=Tb/nb:Tb/nb:Tb;
t2L=length(t2);
x_mod=[];
for i=1:1:N
if x_inp(i)==1
x_mod0=Ac*cos(2*pi*fc*t2+fi1);
else
x_mod0=Ac*cos(2*pi*fc*t2+fi2);
end
x_mod=[x_mod x_mod0];
end
t3=Tb/nb:Tb/nb:Tb*N;
subplot(3,1,2);
plot(t3,x_mod);
xlabel('Time(sec)');
ylabel('Amplitude(volt)');
title('Signal of BPSK modulation');
%Transmitted Signal x
x=x_mod;
h=1;
w=0;
%Received Signal
y=h.*x+w;
%BPSK Demodulation
y_dem=[];
for n=t2L:t2L:length(y)
t=Tb/nb:Tb/nb:Tb;
c=cos(2*pi*fc*t);
y_dem0=c.*y((n-(t2L-1)):n);
t4=Tb/nb:Tb/nb:Tb;
z=trapz(t4,y_dem0);
A_dem=round((2*z/Tb));
if(A_dem>Ac/2)
A=1;
else
A=0;
end
y_dem=[y_dem A];
end
x_out=y_dem;
%Represent output signal as Digital Signal
xx_bit=[];
for n=1:length(x_out)
if x_out(n)==1
xx_bitt=ones(1,nb);
else
xx_bitt=zeros(1,nb);
end
xx_bit=[xx_bit xx_bitt];
end
t4=Tb/nb:Tb/nb:nb*length(x_out)*(Tb/nb);
subplot(3,1,3)
plot(t4,xx_bit,'LineWidth',2);
grid on;
axis([0 Tb*length(x_out) -0.5 1.5]);
ylabel('Amplitude(volt)');
xlabel('Time(sec)');
title('Output Signal as Digital Signal');Output
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