bpsk_qpsk_builtin01.m

Mat lab code of OFDM using BPSK

%   -------------
%    TRANSMITTER
%   -------------

clear all
close all

disp('Here is the code of OFDM using (01)=BPSK ......(02) =QPSK. ');
disp('SET M 2 for BPSK & 4 for QPSK. ');

M = input('Enter value of M 2 = BPSK..... 4 = QPSK etc ... =   ');    

bits = input('enter no of bits ....=  '); ;        
nc = input('enter no of carrier....=  ');                 
len_cp = ceil(0.1*nc);  %   length of cyclic prefix
ifft_points = nc;           
fft_points = nc;
empt=[]; ex1=[];rx=[];
data = randsrc(1, bits, 0:M-1);
figure(1)
stem(data); grid on; 
title('Transmitted Data ')

modulated_data = pskmod(data, M,pi/4);

    for i=1:length(modulated_data);   
     for j=1:nc; 
   ex1=[ex1 modulated_data(:,i)];
   end
    end

figure(1)
scatterplot(ex1);

title('QPSK Modulation')

num_cols=length(ex1)/nc;

data_matrix = reshape(ex1, nc, num_cols);

cp_start = nc-len_cp;
cp_end = nc;


for i=1:num_cols
    ifft_data_matrix(:,i) = ifft((data_matrix(:,i)),ifft_points);
    
    for j=1:len_cp,
       actual_cp(j,i) = ifft_data_matrix(j+cp_start,i);
    end
       ifft_data(:,i) = vertcat(actual_cp(:,i),ifft_data_matrix(:,i));
end

[rows_ifft_data cols_ifft_data]=size(ifft_data)

ofdm_data = rows_ifft_data*cols_ifft_data;

ofdm_signal = reshape(ifft_data, 1, ofdm_data);

figure(3)

plot(real(ofdm_signal)); 
title('Real part of OFDM Signal');
grid on;
figure(4)
plot(imag(ofdm_signal)); 
title('Imaginary part of OFDM Signal');
grid on;


%   ----------
%    Receiver
%   ----------

recvd_signal = ofdm_signal;

%   4.  Convert Data back to "parallel" form to perform FFT
recvd_signal_matrix = reshape(recvd_signal,rows_ifft_data, cols_ifft_data);


%   5.  Remove CP
recvd_signal_matrix(1:len_cp,:)=[];

%   6.  Perform FFT
for i=1:cols_ifft_data,
    %   FFT
    fft_data_matrix(:,i) = fft(recvd_signal_matrix(:,i),fft_points);
end
recvd_serial_data = reshape(fft_data_matrix, 1,bits*nc);
for b=1:nc:length(recvd_serial_data);   
     for m=1:1; 
   rx=[rx recvd_serial_data(:,b)];
   end
end

%   7.  Convert to serial stream
%recvd_serial_data = reshape(rx, 1,bits);

%   8.  Demodulate the data
qpsk_demodulated_data = pskdemod(rx,M);

figure(4)
stem(data)
hold on
stem(qpsk_demodulated_data);
title('Received Data ')
grid on;