www.gusucode.com > MIMO与SISO仿真程序 > MIMO-OFDM/all code/MIMO_v6_5_2x2_ofdma.m
clc; clear all; close all; warning off
data = 2^16; % data points
n_fft = 128; % fft size
n_cp = 16; % cyclic prefix
snr = [0:1:35];
%%
binary_data1 = round(rand(data,1)); % generate data
binary_data2 = round(rand(data,1)); % generate data
h = [randn()+randn()*1i, randn()+randn()*1i; randn()+randn()*1i, randn()+randn()*1i];
% h = [randn()+randn()*1i; randn()+randn()*1i]; % using very different channels for the each of the two
% h = [h h]; % users,
% h = [randn()+randn()*1i];
% h = [h h; h h];
%%
for mod_value = 1:3
% bits per symbol
if mod_value == 1
symbols = 2;
elseif mod_value == 2
symbols = 4;
else
symbols = 6;
while floor(length(binary_data1)/symbols) ~= length(binary_data1)/symbols
binary_data1 = [binary_data1; zeros(1,1)]; %padding for symbol mapping
end
while floor(length(binary_data1)/symbols/n_fft) ~= length(binary_data1)/symbols/n_fft
binary_data1 = [binary_data1; zeros(6,1)]; %padding for subcarriers mapping
end
while floor(length(binary_data2)/symbols) ~= length(binary_data2)/symbols
binary_data2 = [binary_data2; zeros(1,1)]; %padding for symbol mapping
end
while floor(length(binary_data2)/symbols/n_fft) ~= length(binary_data2)/symbols/n_fft
binary_data2 = [binary_data2; zeros(6,1)]; %padding for subcarriers mapping
end
end
mod_method = 2^symbols;
mod_data1 = qammod(binary_data1,mod_method,'unitaveragepower',true,'inputtype','bit');
mod_data2 = qammod(binary_data2,mod_method,'unitaveragepower',true,'inputtype','bit');
%mod_data = mod_data./abs(mod_data);
%% splitting up the data between the transmitters
Tx1 = mod_data1;
Tx2 = mod_data2;
%% subcarriers
Xk1 = reshape(Tx1,n_fft/2,length(Tx1)/(n_fft/2));
Xk2 = reshape(Tx2,n_fft/2,length(Tx2)/(n_fft/2));
Xk1_pad = [ Xk1 ; zeros(size(Xk1)) ];
Xk2_pad = [ zeros( size(Xk2)) ; Xk2 ];
%% ifft
Xn1 = ifft(Xk1_pad);
Xn2 = ifft(Xk2_pad);
%% Cyclic prefix
Xn1_cp = [Xn1(:,(end - n_cp + 1):end),Xn1];
Xn2_cp = [Xn2(:,(end - n_cp + 1):end),Xn2];
%% Channel
% h = [randn()+randn()*1i; randn()+randn()*1i];
for k = 1:length(snr)
yn11 = Xn1_cp*h(1,1); % y time, receiver
yn21 = Xn2_cp*h(2,1);
yn12 = Xn1_cp*h(1,2); % y time, receiver
yn22 = Xn2_cp*h(2,2);
% add noise
yn11 = awgn(yn11,snr(k),'measured');
yn21 = awgn(yn21,snr(k),'measured');
yn12 = awgn(yn12,snr(k),'measured');
yn22 = awgn(yn22,snr(k),'measured');
% superposition of two received signals at receiver
yn1 = yn11 + yn21; % y(1) = h1*x1 + h2*x2 ; y(2) = -h2* x1* + h1 * x2*
yn2 = yn12 + yn22;
%% remove cyclic prefix
yn1_rcp = yn1(:,(n_cp + 1):end);
yn2_rcp = yn2(:,(n_cp + 1):end);
%% DFT
Yk1_block = fft(yn1_rcp);
Yk2_block = fft(yn2_rcp);
% decode sub bands to seperate users
Yk11 = Yk1_block(1:64,:); % higher order decision block
Yk21 = Yk1_block(65:128,:);
Yk12 = Yk2_block(1:64,:);
Yk22 = Yk2_block(65:128,:);
Yk11_s = reshape(Yk11, 1, length(Tx1)); % transform 64 subchannels back into 1 stream
Yk21_s = reshape(Yk21, 1, length(Tx2));
Yk12_s = reshape(Yk12, 1, length(Tx1)); % transform 64 subchannels back into 1 stream
Yk22_s = reshape(Yk22, 1, length(Tx2));
%% Channel estimation
% assume perfect channel estimation, so we know what h1 and h2 are
Xhat11 = Yk11_s./h(1,1);
Xhat21 = Yk21_s./h(2,1);
Xhat12 = Yk12_s./h(1,2);
Xhat22 = Yk22_s./h(2,2);
%% demodulate
X_demod11 = qamdemod(Xhat11,mod_method,'unitaveragepower',true,'outputtype','bit');
X_demod21 = qamdemod(Xhat21,mod_method,'unitaveragepower',true,'outputtype','bit');
output11 = X_demod11(:).';
output21 = X_demod21(:).';
X_demod12 = qamdemod(Xhat11,mod_method,'unitaveragepower',true,'outputtype','bit');
X_demod22 = qamdemod(Xhat21,mod_method,'unitaveragepower',true,'outputtype','bit');
output12 = X_demod12(:).';
output22 = X_demod22(:).';
%%
errors11(mod_value,k) = 0;
for i = 1:length(binary_data1)
if output11(i) ~= binary_data1(i)
errors11(mod_value,k) = errors11(mod_value,k) + 1;
end
end
ber11(mod_value,k) = errors11(mod_value,k)/length(binary_data1);
errors21(mod_value,k) = 0;
for i = 1:length(binary_data2)
if output21(i) ~= binary_data2(i)
errors21(mod_value,k) = errors21(mod_value,k) + 1;
end
end
ber21(mod_value,k) = errors21(mod_value,k)/length(binary_data2);
errors12(mod_value,k) = 0;
for i = 1:length(binary_data1)
if output12(i) ~= binary_data1(i)
errors12(mod_value,k) = errors12(mod_value,k) + 1;
end
end
ber12(mod_value,k) = errors12(mod_value,k)/length(binary_data1);
errors22(mod_value,k) = 0;
for i = 1:length(binary_data2)
if output22(i) ~= binary_data2(i)
errors22(mod_value,k) = errors22(mod_value,k) + 1;
end
end
ber22(mod_value,k) = errors22(mod_value,k)/length(binary_data2);
end
end
semilogy(snr-10*log10(symbols),ber11,'x-',snr,ber21,'^-');
%semilogy(snr,ber11,'x-',snr,ber21,'+-',snr,ber12,'^-',snr,ber22,'v-');
%legend('4QAM user1 Rx1','16QAM user1 Rx1','64QAM user1 Rx1','4QAM user2 Rx1','16QAM user2 Rx1','64QAM user2 Rx1')
%semilogy(snr,ber2(mod_value,:),'o-');
title('OFDMA for 2x2 system receiver 1');
legend('4QAM user1','16QAM user1','64QAM user1','4QAM user2','16QAM user2','64QAM user2')
%'4QAM user1 Rx2','16QAM user1 Rx2','64QAM user1 Rx2','4QAM user2 Rx2','16QAM user2 Rx2','64QAM user2 Rx2');
xlabel('SNR'); ylabel('BER'); grid on
figure()
semilogy(snr,ber12,'+-',snr,ber22,'v-')
%legend('4QAM user1 Rx2','16QAM user1 Rx2','64QAM user1 Rx2','4QAM user2 Rx2','16QAM user2 Rx2','64QAM user2 Rx2');
title('OFDMA for 2x2 system receiver 2');
legend('4QAM user1','16QAM user1','64QAM user1','4QAM user2','16QAM user2','64QAM user2');
xlabel('SNR'); ylabel('BER'); grid on