to plot graph of SNR Vs BER of QPSK based MIMO OFDM system

Hello all......

i am trying to implement the QPSK based MIMO OFDM System and want to plot graph of SNR vs BER of the same . i am not getting it as a proper graph. kindly help me in this regards

M=4;
k=log2(M); % number of bits/symbol
number_of_data_points=64;         % FFT Size or total number of subcarriers=N=64= IFFT size
block_size=16;                    % Block Size, no of rows,data subcarriers
BW=8*10^6;                       % Bandwidth of the OFDM system
Nsp=52;
%Derived Parameters
deltaf=BW/number_of_data_points;%bandwidth of each subcarriers including used and unused subacarriers
TFFT=1/deltaf;                  % ofdm_symbol_duration
TGI=TFFT/4;                     % duration of the cyclic prefix= guard interval duration 25% of the subcarriers to be used as a GI
% possible guard band values 1/4, 1/8, 1/16 and 1/32
Tsignal= TGI+TFFT ;             % total ofdm symbol duration
Ncp=number_of_data_points*(TGI/TFFT); % length of the cyclic prefix
cp_len=ceil(0.25*block_size);
fft_points=number_of_data_points;
ifft_points=number_of_data_points;
Nt=2;
Nr=2;
cp_start=block_size-cp_len;        
cp_end=block_size;                  
actual_cp=zeros(cp_len, block_size);
data_subcarriers=cp_start+Nsp;
nsf=8/7;
Fs=ceil(nsf*BW);
% initialization of SNR 
SNRstart=0;
SNRincrement=1;
SNRend=25;
index=0;
%-------------------------------------------------------------------------%
%1.  1st Block -Implementation of binary data                              %
%1st Block -Implementation of bianry data- generation                     %
%-------------------------------------------------------------------------%
x1=randi([0 1],1,64);
br=BW; %Let us transmission bit rate  1000000
fc=br; % minimum carrier frequency
Tc=1/br; % bit duration
tmod=Tc/99:Tc/99:Tc; % Time vector for one bit information
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%-------------------------------------------------------------------------%
%------- encoded data by using LDPC Encoder and Parity Check Matrix-------%
%-------------------------------------------------------------------------%
data_encoded=x1*H;
mod_data=mod(data_encoded,2);
%-------------------------------------------------------------------------%
%---------3. modulation of the data by using psk------------------------- %
%-------------------------------------------------------------------------%

data_NRZ=2*mod_data-1; % Data Represented at NZR form for QPSK modulation
s_p_data=reshape(data_NRZ,2,length(x1)/2);  % S/P convertion of data
ymod=[];
ycomplex=[];
y_in=[];
y_qd=[];
for imod = 1:length(x1)/2
    y1 = s_p_data(1,imod)*cos(2*pi*fc*tmod); % inphase component
    y2 = s_p_data(2,imod)*sin(2*pi*fc*tmod) ;% Quadrature component
    y_in = [y_in y1]; % inphase signal vector
    y_qd = [y_qd y2]; %quadrature signal vector
    ymod=[ymod y1+y2]; % modulated signal vector
    ycomplex = [ycomplex (sign(y1))+(1i*sign(y2))];
end
psk_mod=ycomplex;
Tx_sig1=ymod; % transmitting signal after modulation
Tx_sig=ycomplex; % transmitting signal after modulation
Tx_sig_complex=ycomplex;
ttmod=Tc/99:Tc/99:(Tc*length(x1))/2;
% to  find out the number of columns after reshaping
num_colums=(size(Tx_sig_complex,1)*size(Tx_sig_complex,2))/block_size;   
%-------------------------------------------------------------------------%
%              5.to perform serial to parallel conversion                 %
%-------------------------------------------------------------------------%
reshaped_mod_data = reshape(Tx_sig1,[block_size, num_colums]);
%-------------------------------------------------------------------------%
%            6.     To Perform IFFT and Cyclic Prefix                     %
%                 to create empty matrix to put ifft data                 %
% 7.operate column wise and do cyclic prefix, column wise cyclic prefix is done
%-------------------------------------------------------------------------%

for ireshape=1:num_colums
    ifft_data_matrix(:,ireshape)=ifft(reshaped_mod_data(:,ireshape)); 
    for jcplen= 1:cp_len  % compute cyclic prefix data
        actual_cp(jcplen,ireshape) = ifft_data_matrix(jcplen+cp_start,ireshape).';
    end
    ifft_data_after_cp(:,ireshape) = vertcat(actual_cp(:,ireshape),ifft_data_matrix(:,ireshape));% perform cyclic prefix
end
%-------------------------------------------------------------------------%
%           8.    to perform parallel to serial conversion                %            
%-------------------------------------------------------------------------%
parallel_serial_tx = reshape(ifft_data_after_cp(:,:),size(ifft_data_after_cp(:,:),2),size(ifft_data_after_cp(:,:),1));
%-------------------------------------------------------------------------%
%          12. To find the number of rows and colums after ifft           %
%-------------------------------------------------------------------------%

[ifft_rows,ifft_colums]=size(parallel_serial_tx);
ofdm_length=ifft_rows*ifft_colums;              
%-------------------------------------------------------------------------%
%       to convert to serial stream for to obtain OFDM Signal          %
%                       to generate ofdm signal - begin                   %
%-------------------------------------------------------------------------%
ofdm_signal= reshape(parallel_serial_tx,1,ofdm_length) ;% serial_parallel_form = reshape( b,block_size,num_colums) ;1x130
received_bits=zeros(size(SNRstart:SNRincrement:SNRend));
index=0;
for snr=SNRstart:SNRincrement:SNRend
    index=index+1;
%creation of multipath channel
channel = randn(size(parallel_serial_tx))+sqrt(-1)*randn(size(parallel_serial_tx));

% Pass the signal thru the channel

after_channel = filter(reshape(channel,1,[]),1,ofdm_signal);

%generate AWGN noise
awgn_noise=awgn(after_channel,snr,'measured');

% received signal

received_signal = after_channel+awgn_noise;

% To perform Serial to Parallel Conversion

serial_parallel_form_rx = reshape(received_signal,[ifft_rows,ifft_colums]).';%64x2

%To Remove Cyclic Prefix
serial_parallel_form_rx(1:cp_len,:,:)=[];

% To Perform FFT operation
receivd_signal_fft_rx=fft(serial_parallel_form_rx);
 %  To Perform Parallel to Serial Conversion
 parallel_serial_form_rx= reshape(receivd_signal_fft_rx,1,[]);
  %  To pass through Demodulator
Rx_data=[];
Rx_sig=parallel_serial_form_rx; % Received signal
Rx_sig_real=sign(real(Rx_sig));
Rx_sig_imag=sign(imag(Rx_sig));
for (idemod=1:1:length(x1)/2)
    %%XXXXXX inphase coherent dector XXXXXXX
         Z_in=Rx_sig_real((idemod-1)*length(tmod)+1:idemod*length(tmod)).*cos(2*pi*fc*tmod);   
%          Z_in=Rx_sig_real(((idemod-1)*length(tmod)+1:idemod*length(tmod)).*cos(2*pi*fc*tmod));
%         Z_in=Rx_sig_real((idemod-1)*length(tmod)+1:}.2demod*length(tmod)).*cos(2*pi*fc*tmod); 
    % above line indicat multiplication of received & inphase carred signal
    
    Z_in_intg=(trapz(tmod,Z_in))*(2/Tc);% integration using trapizodial rull
    if(Z_in_intg>0) % Decession Maker
       Rx_in_data=1;
    else
       Rx_in_data=0; 
    end
    
    %%XXXXXX Quadrature coherent dector XXXXXX
    Z_qd=Rx_sig_imag(((idemod-1)*length(tmod))+1:idemod*length(tmod)).*sin(2*pi*fc*tmod);
    %above line indicat multiplication ofreceived & Quadphase carred signal
    
    Z_qd_intg=(trapz(tmod,Z_qd))*(2/Tc);%integration using trapizodial rull
        if (Z_qd_intg>0)% Decession 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
psk_demod_mod=Rx_data;
Hinv=H.';
rece_decoder=psk_demod_mod*Hinv;
rece_decoder_mod=mod(rece_decoder,2);
% [n, received_bits(index)]=biterr(x1,psk_demod_mod);
[n, received_bits(index)]=biterr(x1,rece_decoder_mod);
end
snr=SNRstart:SNRincrement:SNRend;
%% Plotting BER vs SNR
figure (6)
semilogy(snr,(received_bits),'-ok');
grid;
title('OFDM Bit Error Rate .VS. Signal To Noise Ratio');
ylabel('BER');
xlabel('SNR [dB]');

[KALYAN ACHARJYA]

Can you show us the expected graph?

[ABDUL]

[ABDUL]

the graph should be obeying the standard BER values .

[Ivancica Ram]

Hi, did you resolve this problem ?

[ABDUL]

no sir i didnt get it

[Mohamad Bayaa]

im finding the same issue did you get the answer?

[ABDUL]

no i didnt get .... if you get it help me out ..

Answer 1

[Maryan Yousif]

Hi, did you solve the problem, if you solved the problem please can you please show me how you solved, thanks.

[ABDUL]

no i didnt get the solution

[ABDUL]

if you can help me out in this will be off great help

Answer 2

[sonia benabdallah]

hey please i have a question for you.I couldn't have the same figure as you.

[Sobia Omer]

Did you get the solution how to correctly plot the semilog?