Little improvement, I added AWGN plus minor changes

[abusous2000]

Hi

Many thanks for this great program. I am new to Matlab and learned alot from your example; especially that it is bit using communication package.

Anyhow, I decide to add noise & error rate calculations, plus added little improvements that others may find helpful

%XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
%XXXX QPSK Modulation and Demodulation without consideration of noise XXXXX
%XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
clc;
clear all;
close all;
data=[0 1 0 1 1 1 0 0 1 1]; % information
ebNo = -60;

%Number_of_bit=1024;
%data=randint(Number_of_bit,1);

figure(1)
stem(data, 'linewidth',3), grid on;
title('  Information before Transmitting ');
axis([ 0 11 0 1.5]);

data_NZR=2*data-1; % Data Represented at NZR form for QPSK modulation
s_p_data=reshape(data_NZR,2,length(data)/2);  % S/P conversion of data


br=10.^6; %Let us transmission bit rate  1000000
f=br; % minimum carrier frequency
T=1/br; % bit duration
t=T/100:T/100:T; % Time vector for one bit information

% XXXXXXXXXXXXXXXXXXXXXXX QPSK modulatio  XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
y=[];
y_in=[];
y_qd=[];
for(i=1:length(data)/2)
    y1=s_p_data(1,i)*cos(2*pi*f*t); % inphase component
    y2=s_p_data(2,i)*sin(2*pi*f*t) ;% Quadrature component
    y_in=[y_in y1]; % inphase signal vector
    y_qd=[y_qd y2]; %quadrature signal vector
    y=[y y1+y2]; % modulated signal vector
end

channel = comm.AWGNChannel('EbNo',ebNo,'BitsPerSymbol',2);
errorRate = comm.ErrorRate;
%Tx_sig=y; % transmitting signal after modulation
Tx_sig=channel(y);
tt=T/100:T/100:(T*length(data))/2;

figure(2)

subplot(3,1,1);
plot(tt,y_in,'linewidth',3), grid on;
title(' wave form for inphase component in QPSK modulation ');
xlabel('time(sec)');
ylabel(' amplitude(volt0');

subplot(3,1,2);
plot(tt,y_qd,'linewidth',3), grid on;
title(' wave form for Quadrature component in QPSK modulation ');
xlabel('time(sec)');
ylabel(' amplitude(volt0');


subplot(3,1,3);
plot(tt,Tx_sig,'r','linewidth',3), grid on;
title('QPSK modulated signal (sum of inphase and Quadrature phase signal)');
xlabel('time(sec)');
ylabel(' amplitude(volt0');

% XXXXXXXXXXXXXXXXXXXXXXXXXXXX QPSK demodulation XXXXXXXXXXXXXXXXXXXXXXXXXX
Rx_data=[];
Rx_sig=Tx_sig; % Received signal
Z_intg_Mtx = [];
for(i=1:1:length(data)/2)

    %XXXXXX inphase coherent dector XXXXXXX
    Z_in=Rx_sig((i-1)*length(t)+1:i*length(t)).*cos(2*pi*f*t); 
    % above line indicates multiplication of received & inphase carried signal
    
    Z_in_intg=(trapz(t,Z_in))*(2/T);% integration using trapezoidal rule
    Z_intg_Mtx(1,i) = Z_in_intg;
    if(Z_in_intg>0) % Decision Maker
        Rx_in_data=1;
    else
       Rx_in_data=0; 
    end
    
    %XXXXXX Quadrature coherent dector XXXXXX
    Z_qd=Rx_sig((i-1)*length(t)+1:i*length(t)).*sin(2*pi*f*t);
    %above line indicates multiplication o the received & Quad Phase carried signal
    
    Z_qd_intg=(trapz(t,Z_qd))*(2/T);%integration using trapezoidal rule
    Z_intg_Mtx(2,i) = Z_qd_intg;
    if (Z_qd_intg>0)% Decision Maker
       Rx_qd_data=1;
    else
       Rx_qd_data=0; 
    end
    
    
    Rx_data=[Rx_data  Rx_in_data  Rx_qd_data]; % Received Data vector
end


figure(3)
stem(Rx_data,'linewidth',3) 
title('Information after Receiving ');
axis([ 0 11 0 1.5]), grid on;

errorStats = errorRate(data',Rx_data');

errorStats(1);

% XXXXXXXXXXXXXXXXXXXXXXXXX    end of program    XXXXXXXXXXXXXXXXXXXXXXXXXX

Cheers

[Mithilesh1609]

thanks for this wonderful inclusion