基于STBC的MIMO-OFDM系统

function [BER] = STBC_2x2(SNR_Range,NFFT,frame) s_Num = NFFT; %导频及数据位置 %等间距 pilot_num = 0; pilot_pos = []; data_pos = 1:1:s_Num/2; for ii=1:length(SNR_Range) SNR=SNR_Range(ii) error_num_bin=0; for j = 1:1:frame M=4; x = randi([0 M-1],(NFFT - pilot_num*2),1);%生产随机信号 symbol_bin = qammod(x,M); x1 = zeros(NFFT,1); x2 = zeros(NFFT,1); x1(pilot_pos,1)=1; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% stbc %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% x1((NFFT/2)+1:end,:) = conj( x1(1:NFFT/2,:)); pilot_pos = find(x1 ~= 0); x1(data_pos,1)=symbol_bin(1:length(data_pos),1); x1((NFFT/2)+1:end,:) = conj( x1(1:NFFT/2,:)); x2(data_pos,1)=symbol_bin((length(data_pos)) + 1:end,1); x2(pilot_pos,1)=0; x2((NFFT/2)+1:end,:) = conj( x2(1:NFFT/2,:)); cx2=(-conj(x2)); cx1=conj(x1); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% ifft %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% t_x1 = ifft(x1); t_x2 = ifft(x2); t_cx2 = ifft(cx2); t_cx1 = ifft(cx1); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 多径信道 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% a11=[0.11 0.13 0.21 0.16 0.15]; %多径的幅度 d11=[3 5 7 11 14]; %各径的延迟 a12=[0.11 0.09]; %多径的幅度 d12=[2 8]; %各径的延迟 a21=[0.11 0.1]; %多径的幅度 d21=[4 9]; %各径的延迟 a22=[0.1 0.09]; %多径的幅度 d22=[6 12]; %各径的延迟 x1 = [t_x1;t_cx2]; x2 = [t_x2;t_cx1]; [x11,h11]=multipath_mimo(NFFT,x1,a11,d11); [x22,h12]=multipath_mimo(NFFT,x2,a12,d12); [yx11,h21]=multipath_mimo(NFFT,x1,a21,d21); [yx22,h22]=multipath_mimo(NFFT,x2,a22,d22); y11_bin00 = x11 + x22;%第一个时刻x1 y11_bin00（1:nfft,:） y12_bin00 = yx11 + yx22;%第二个时刻x2 y12_bin00（1:nfft,:） y11_bin0 = y11_bin00(1:NFFT,:); y21_bin0 = y11_bin00(NFFT+1:end,:); y12_bin0 = y12_bin00(1:NFFT,:); y22_bin0 = y12_bin00(NFFT+1:end,:); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 加噪声 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% s_Num = NFFT; TxSymbol(:,1) = [y11_bin0;y21_bin0]; TxSymbol(:,2) = [y12_bin0;y22_bin0]; SignalPower=sum(sum(abs(TxSymbol(:,1).*TxSymbol(:,1))))/(length(TxSymbol(:,1))); % Twice MRRC power NoisePower=SignalPower*10^(-0.65*SNR/10); attn=sqrt(NoisePower); r1 = (randn(s_Num*2,1)+1i*randn(s_Num*2,1)); AWGNoise1=1/sqrt(2)*r1*attn; SignalPower2=sum(sum(abs(TxSymbol(:,2).*TxSymbol(:,2))))/(length(TxSymbol(:,2))); % Twice MRRC power NoisePower2=SignalPower2*10^(-0.65*SNR/10); attn2=sqrt(NoisePower2); r2 = (randn(s_Num*2,1)+1i*randn(s_Num*2,1)); AWGNoise2=1/sqrt(2)*r2*attn2; y11_bin = y11_bin0 + AWGNoise1(1:NFFT,1); y12_bin = y12_bin0 + AWGNoise2(1:NFFT,1); y21_bin = y21_bin0 + AWGNoise1(NFFT+1:end,1); y22_bin = y22_bin0 + AWGNoise2(NFFT+1:end,1); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Y11_bin = fft(y11_bin); Y12_bin = fft(y12_bin); Y21_bin = fft(y21_bin); Y22_bin = fft(y22_bin); h = [h11,h12,h21,h22]; H = fft(h); H11 = H(:,1); H12 = H(:,2); H21 = H(:,3); H22 = H(:,4); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% s1_bin = zeros(NFFT,2); for z = 1:1:NFFT s1_bin(z,1)=(conj(H11(z)).*Y11_bin(z)+H12(z).*conj(Y21_bin(z))+conj(H21(z)).*(Y12_bin(z))+H22(z).*conj(Y22_bin(z))); s1_bin(z,2)=(conj(H12(z)).*Y11_bin(z)-H11(z).*conj(Y21_bin(z))+conj(H22(z)).*(Y12_bin(z))-H21(z).*conj(Y22_bin(z))); end re_data = s1_bin(data_pos,:); s1_bin1 = reshape(re_data,[],1); output_qpsk_alamouti_bin = qamdemod(s1_bin1,M); % Check symbol error rate. [num_bin,~] = biterr(x,output_qpsk_alamouti_bin); error_num_bin = error_num_bin + num_bin; end BER_alamouti_bin=error_num_bin/(frame*128*2); BER(ii)=BER_alamouti_bin; end end