Matlab code simulation of mimo2*2 ofdm with stbc

Hello everybody, I am student in telecom, and I evolves on a subject bringing on the simulation of a mimo transmission chain (2*2) ofdm with stbc code. and i need help to write ecripts of simulation, so if someone has some programs wich can help me, please post theme here thnks ( sorry for my english)

[Rayhan]

clc; clear; close all;

% Parameters
N = 64;             % FFT size
cpLen = 16;         % Cyclic prefix length
numSymbols = 1000;  % Number of OFDM symbols
SNR_dB = 0:5:30;    % SNR range in dB

% Modulation (QPSK)
mod_order = 4;
M = log2(mod_order);
data = randi([0 1], 2*N*numSymbols*M, 1);
dataSym = qammod(reshape(data, [], M)*2.^(M-1:-1:0).', mod_order, 'InputType', 'integer');

% STBC Alamouti Encoding
dataSym = reshape(dataSym, 2, []);  % Pair symbols for STBC
x1 = dataSym(1,:);
x2 = dataSym(2,:);
s1 = x1; s2 = x2;
s3 = -conj(x2); s4 = conj(x1);

% IFFT for OFDM
s1_OFDM = ifft(reshape(s1, N, []), N);
s2_OFDM = ifft(reshape(s2, N, []), N);
s3_OFDM = ifft(reshape(s3, N, []), N);
s4_OFDM = ifft(reshape(s4, N, []), N);

% Add CP
s1_OFDM = [s1_OFDM(end-cpLen+1:end, :); s1_OFDM];
s2_OFDM = [s2_OFDM(end-cpLen+1:end, :); s2_OFDM];
s3_OFDM = [s3_OFDM(end-cpLen+1:end, :); s3_OFDM];
s4_OFDM = [s4_OFDM(end-cpLen+1:end, :); s4_OFDM];

% Transmit through Rayleigh Channel
BER = zeros(size(SNR_dB));
for snrIdx = 1:length(SNR_dB)
    snr = 10^(SNR_dB(snrIdx)/10);
    
    % Channel (flat fading per subcarrier)
    h11 = (randn(1, size(s1,2)) + 1j*randn(1, size(s1,2))) / sqrt(2);
    h12 = (randn(1, size(s1,2)) + 1j*randn(1, size(s1,2))) / sqrt(2);
    h21 = (randn(1, size(s1,2)) + 1j*randn(1, size(s1,2))) / sqrt(2);
    h22 = (randn(1, size(s1,2)) + 1j*randn(1, size(s1,2))) / sqrt(2);
    
    % Transmit two time slots
    y1 = h11 .* s1 + h12 .* s2;
    y2 = h21 .* s1 + h22 .* s2;
    y3 = h11 .* s3 + h12 .* s4;
    y4 = h21 .* s3 + h22 .* s4;
    
    % Noise
    noise = @(x) x + sqrt(1/(2*snr))*(randn(size(x)) + 1j*randn(size(x)));
    y1 = noise(y1); y2 = noise(y2);
    y3 = noise(y3); y4 = noise(y4);
    
    % Receiver: Alamouti decoding (per subcarrier)
    r1 = conj(h11).*y1 + h12.*conj(y3);
    r2 = conj(h21).*y2 + h22.*conj(y4);
    r3 = conj(h12).*y1 - h11.*conj(y3);
    r4 = conj(h22).*y2 - h21.*conj(y4);
    
    s1_hat = r1 + r2;
    s2_hat = r3 + r4;
    
    % Combine
    rxSym = [s1_hat; s2_hat];
    rxSym = reshape(rxSym, [], 1);
    
    % Demodulate
    rxBits = de2bi(qamdemod(rxSym, mod_order, 'OutputType', 'integer'), M);
    rxBits = reshape(rxBits.', [], 1);
    
    % BER
    BER(snrIdx) = mean(data ~= rxBits(1:length(data)));
end

% Plot
figure;
semilogy(SNR_dB, BER, '-o');
xlabel('SNR (dB)'); ylabel('Bit Error Rate');
title('2x2 MIMO-OFDM STBC (QPSK)');
grid on;

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