Code covered by the BSD License

### Nikesh Bajaj (view profile)

ASK, PSK, FSK modulation and BER vs SNR calculation

%msglen= number of bits to be transmitted
%take msglen=10000, or 20000 for more accuracy
%%===============================================
% NIKESH BAJAJ
% Asst. Prof., Lovely Professional University, India
% Almameter: Aligarh Muslim University, India
% +919915522564, bajaj.nikkey@gmail.com
%%===============================================
n=msglen;
b=randint(1,n);
f1=1;f2=2;
t=0:1/30:1-1/30;
sa1=sin(2*pi*f1*t);
E1=sum(sa1.^2);
sa1=sa1/sqrt(E1); %unit energy
sa0=0*sin(2*pi*f1*t);
%FSK
sf0=sin(2*pi*f1*t);
E=sum(sf0.^2);
sf0=sf0/sqrt(E);
sf1=sin(2*pi*f2*t);
E=sum(sf1.^2);
sf1=sf1/sqrt(E);
%PSK
sp0=-sin(2*pi*f1*t)/sqrt(E1);
sp1=sin(2*pi*f1*t)/sqrt(E1);

%MODULATION
for i=1:n
if b(i)==1
psk=[psk sp1];
fsk=[fsk sf1];
else
psk=[psk sp0];
fsk=[fsk sf0];
end
end
figure(1)
subplot(411)
stairs(0:10,[b(1:10) b(10)],'linewidth',1.5)
axis([0 10 -0.5 1.5])
title('Message Bits');grid on
subplot(412)
tb=0:1/30:10-1/30;
subplot(413)
plot(tb, fsk(1:10*30),'r','linewidth',1.5)
title('FSK Modulation');grid on
subplot(414)
plot(tb, psk(1:10*30),'k','linewidth',1.5)
title('PSK Modulation');grid on
xlabel('Time');ylabel('Amplitude')
%AWGN
for snr=0:20
pskn=awgn(psk,snr);
fskn=awgn(fsk,snr);

%DETECTION
A=[];F=[];P=[];
for i=1:n
A=[A 1];
else
A=[A 0];
end
%FSK Detection
if sum(sf1.*fskn(1+30*(i-1):30*i))>0.5
F=[F 1];
else
F=[F 0];
end
%PSK Detection
if sum(sp1.*pskn(1+30*(i-1):30*i))>0
P=[P 1];
else
P=[P 0];
end
end

%BER
errA=0;errF=0; errP=0;
for i=1:n
if A(i)==b(i)
errA=errA;
else
errA=errA+1;
end
if F(i)==b(i)
errF=errF;
else
errF=errF+1;
end
if P(i)==b(i)
errP=errP;
else
errP=errP+1;
end
end
BER_A(snr+1)=errA/n;
BER_F(snr+1)=errF/n;
BER_P(snr+1)=errP/n;
end

figure(2)
subplot(411)
stairs(0:10,[b(1:10) b(10)],'linewidth',1.5)
axis([0 10 -0.5 1.5]);grid on
subplot(412)
tb=0:1/30:10-1/30;
subplot(413)
plot(tb, fskn(1:10*30),'r','linewidth',1.5)
subplot(414)
plot(tb, pskn(1:10*30),'k','linewidth',1.5)
figure(3)
semilogy(0:20,BER_A, 'b','linewidth',2)
title('BER Vs SNR')
grid on;
hold on
semilogy(0:20,BER_F,'r','linewidth',2)
semilogy(0:20,BER_P, 'k','linewidth',2)
xlabel('Eo/No(dB)')
ylabel('BER')
hold off