DPSK_Signaling.m

%Shift Keying Techniques - DPSK
clc
clear all
close all
M=2;  %Alphabet size
N=input("Enter the no. of symbols:");  %number of symbols
nb=log(M)/log(2);  %number of bits/symbol

%Transmitter
%bit generation
b=randi([0 1],N*nb,1);  %Random binary bits
dpskmod=comm.DPSKModulator(2,pi/2,'BitInput',true);
dpskdemod=comm.DPSKDemodulator(2,pi/2,'BitOutput',true);

yx=dpskmod(b); %only for simulation
scatterplot(yx);

SNRdB=1:7:15;
for ii=1:length(SNRdB)
    SNRii=SNRdB(ii);
    rn=awgn(yx,SNRii,'measured');
    figure; plot(real(rn),imag(rn),'b.',real(yx),imag(yx),'ro');legend('received','ideal');
    xlabel("Real"); ylabel("Imaginary");
    title(['DPSK constellation @ SNR=' num2str(SNRii),' dB']); axis([-3.5 3.5 -3.5 3.5]);
    
    bcat=dpskdemod(rn);
    
    snr=10^(SNRii./10);
    Eb_by_No=snr;
    Eb_by_No_dB(ii)=10*log10(Eb_by_No);
    BER_th(ii)=1/2*exp(-Eb_by_No);
    BER(ii)=length(find(b~=bcat))/(N*nb);
end
figure;
semilogy(Eb_by_No_dB,BER,'b--',Eb_by_No_dB,BER_th,'r*');
axis([0 12 10^-7 1]);grid on;
xlabel('E_b/N_o (dB)'); ylabel('Bit error probability (P_e)');
title('BER performance of QPSK');