实现Alamouti码的代码

%=================================================================== %10/30/04 Sun Jie-ting ECUST %=================================================================== % Alamouti.m % ========== % Description: This m-file simulates the SER performance of Alamouti % space-time shceme using maximum likelihood decoding % Usage: ser_ml=Alamouti(Nr,max_snr,max_err_symbol,symbol_per_frame) % Inputs: % Nr: the number of receiving antenna,either 1 or 2 % max_snr: simulation from 0 to max_snr % max_err_symbol: the simulation will stop when the number of % received error symbols exceeds max_err_symbol % symbol_per_frame: the number of symbols to transmit in a data % frame and we assume the channel fading % coefficients will keep the same the data % frame transmitting period.Becasue of 2 Tx % antenna, symbol_per_frame must be even % Outputs: % ser_ml: symbol-error-ratio of each snr % ====================================================================== %function ser_ml=Alamouti(Nr,max_snr,max_err_symbol,symbol_per_frame); %clc; %发射天线数，固定为2 %if mod(symbol_per_frame,2) == 0 clear; Nt = 2; Nr=1; max_snr=20; symbol_per_frame=4096; H=RayleighCH(Nr,Nt); tot_frame_tx=zeros(1,max_snr+1); tot_err_symbol =zeros(1,max_snr+1); tot_frame_tx = zeros(1,max_snr+1); for snr=0:max_snr %while tot_err_symbol(snr+1)<max_err_symbol %tot_frame_tx(snr+1) = tot_frame_tx(snr+1)+1; %生成伪随机二进制待发送序列 psudo_bit_sequence = rand(1,symbol_per_frame * 2)>0.5; %二进制信道与QPSK信号的转换 qpsk_sequence = QpskMapping(psudo_bit_sequence); %噪声能量（已归一化） % sig = sqrt(0.5/(10^(snr/10))); sig = sqrt(1/(10^(snr/10))); %生成加性高斯噪声 addtional_gaussian_noise = sig * (randn(Nr,Nt,symbol_per_frame) + j*randn(Nr,Nt,symbol_per_frame)); %生成具有瑞利分布特性的信道衰落系数 %H=RayleighCH(Nr,Nt); for k=1:2:symbol_per_frame-1 X=[qpsk_sequence(k) -conj(qpsk_sequence(k+1)); qpsk_sequence(k+1) conj(qpsk_sequence(k))]; %接收信号 R=H*X + addtional_gaussian_noise(:,:,k); %接收信号的合成（利用发送矩阵的正交性对信道衰落矩阵进行正交化处理），由Alamoui码原理可知，信号合成方式因接收天线数目而异 switch Nr case 1 s0=conj(H(1))*R(1)+H(2)*conj(R(2)); s1=conj(H(2))*R(1)-H(1)*conj(R(2)); case 2 s0=conj(H(1,1))*R(1,1)+H(1,2)*conj(R(1,2))+conj(H(2,1))*R(2,1)+H(2,2)*conj(R(2,2)); s1=conj(H(1,2))*R(1,1)-H(1,1)*conj(R(1,2))+conj(H(2,2))*R(2,1)-H(2,1)*conj(R(2,2)); end S=[s0 s1]; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 最大似然译码 % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% dh = [1+j -1+j -1-j 1-j]/sqrt(2); D1=abs(S(1)*[1 1 1 1]-dh).^2; [minScale positionmin]=min(D1); X_dec1=dh(positionmin); D2=abs(S(2)*[1 1 1 1]-dh).^2; [minScale positionmin]=min(D2); X_dec2=dh(positionmin); X_dec=[X_dec1;X_dec2]; if sum([(X(1,1)~=X_dec1) X(2,1)~=X_dec2])%if sum([round(X(1,1)~=X_dec1) X(2,1)~=X_dec2]) tot_err_symbol(snr+1)=tot_err_symbol(snr+1)+1; break end end %end end %在不同信噪比条件下，求系统SER（误符号率） ser_ml=tot_err_symbol./(symbol_per_frame); % [minScale positionmin] = min(ser_ml); plot(ser_ml,'o-'); xlabel('SNR'); ylabel('Symbol Error Ratio(SER)'); grid on; %axis([0 max_snr 10^(round(log10(minScale)-0.5)) 1]); %else %disp('symbol_per_frame must be even!'); %ser_ml = 0; %end