ostbc4.m

MIMO-有关差分编码,用matlab书写,

function OSTBC4
    Nt=4;%发射天线数为4
    Nr=1;%接收天线数为1
    max_snr=20;%最大的信噪设定为15
    symbol_per_frame=120;%每一帧的符号数为120个
    tot_frame_tx=zeros(1,max_snr+1);
    tot_err_bit=zeros(1,max_snr+1);
    tot_err_symbol=zeros(1,max_snr+1);
   for snr=0:max_snr 
           sig =sqrt(4/(10^(snr/10))); 
        for ii=0:1000
             tot_frame_tx(snr+1) = tot_frame_tx(snr+1)+1;
             bit_sequence = rand(1,symbol_per_frame * 2)>0.5;        %生成伪随机二进制待发送序列
             qpsk_sequence = QpskMapping(bit_sequence); %二进制信道与QPSK信号的转换
           %归一化的噪声能量       
            addtional_gaussian_noise =sig * (randn(Nr,Nt,symbol_per_frame/3) + j*randn(Nr,Nt,symbol_per_frame/3))/sqrt(2); %生成加性高斯噪声
            H=RayleighCH(Nr,Nt); %生成具有瑞利分布特性的信道衰落系数
            for k=1:3:(symbol_per_frame-3)
                M=1;
                X=[qpsk_sequence(k)        -conj(qpsk_sequence(k+1))            conj(qpsk_sequence(k+2))/sqrt(2)                conj(qpsk_sequence(k+2))/sqrt(2); 
                   qpsk_sequence(k+1)      conj(qpsk_sequence(k))            conj(qpsk_sequence(k+2))/sqrt(2)                  -conj(qpsk_sequence(k+2))/sqrt(2); 
                   qpsk_sequence(k+2)/sqrt(2)  qpsk_sequence(k+2)/sqrt(2)  (-qpsk_sequence(k)-conj(qpsk_sequence(k))+qpsk_sequence(k+1)-conj(qpsk_sequence(k+1)))/2  (qpsk_sequence(k+1)+conj(qpsk_sequence(k+1))+qpsk_sequence(k)-conj(qpsk_sequence(k)))/2; 
                   qpsk_sequence(k+2)/sqrt(2)  -qpsk_sequence(k+2)/sqrt(2)  (-qpsk_sequence(k+1)-conj(qpsk_sequence(k+1))+qpsk_sequence(k)-conj(qpsk_sequence(k)))/2  -(qpsk_sequence(k)+conj(qpsk_sequence(k))+qpsk_sequence(k+1)-conj(qpsk_sequence(k+1)))/2;];
                R=H*X+addtional_gaussian_noise(:,:,M);  %接收信号
                M=M+1;      
                x1=R(1,1)*conj(H(1,1))+conj(R(1,2))*H(1,2)+(R(1,4)-R(1,3))*(conj(H(1,3))-conj(H(1,4)))/2-conj(R(1,4)+R(1,3))*(H(1,3)+H(1,4))/2;   
                x2=R(1,1)*conj(H(1,2))-conj(R(1,2))*H(1,1)+(R(1,4)+R(1,3))*(conj(H(1,3))-conj(H(1,4)))/2+conj(R(1,4)-R(1,3))*(H(1,3)+H(1,4))/2;   
                x3=((R(1,1)+R(1,2))*conj(H(1,3))+(R(1,1)-R(1,2))*conj(H(1,4))+conj(R(1,3))*(H(1,1)+H(1,2))+conj(R(1,4))*(H(1,1)-H(1,2)))/sqrt(2);
                dh = [1+j -1+j -1-j 1-j]/sqrt(2);
                D1=abs(x1*[1 1 1 1]-dh).^2;
                [minnumber1 position1]=min(D1);%求出最小的距离
                X1=dh(position1);             %估计出x1的值
                D2=abs(x2*[1 1 1 1]-dh).^2;
                [minnumber1 position2]=min(D2);
                X2=dh(position2);
                D3=abs(x3*[1 1 1 1]-dh).^2;
                [minnumber1 position3]=min(D3);
                X3=dh(position3);
                if(X(1,1)~=X1)  %计算自然循序mapping时bit错误的个数
                     tot_err_symbol(snr+1)=tot_err_symbol(snr+1)+1;
                   if((X(1,1)+X1)*sqrt(2)==2|(X(1,1)+X1)*sqrt(2)==-2)
                    tot_err_bit(snr+1)=tot_err_bit(snr+1)+2;
                   else
                          tot_err_bit(snr+1)=tot_err_bit(snr+1)+1; 
                     end
                  end
                 if(X(2,1)~=X2)
                      tot_err_symbol(snr+1)=tot_err_symbol(snr+1)+1;
                    if((X(2,1)+X2)*sqrt(2)==2|(X(2,1)+X2)*sqrt(2)==-2)
                    tot_err_bit(snr+1)=tot_err_bit(snr+1)+2;
                     else
                      tot_err_bit(snr+1)=tot_err_bit(snr+1)+1; 
                    end   
                 end
                  if(X(3,1)*sqrt(2)~=X3)
                      tot_err_symbol(snr+1)=tot_err_symbol(snr+1)+1;
                    if((X(3,1)*sqrt(2)+X3)*sqrt(2)==2|(X(3,1)*sqrt(2)+X3)*sqrt(2)==-2)
                    tot_err_bit(snr+1)=tot_err_bit(snr+1)+2;
                     else
                      tot_err_bit(snr+1)=tot_err_bit(snr+1)+1; 
                    end   
                 end
           end
        end
    end        
    %在不同信噪比条件下，求系统SER和BER
    ser_snr=tot_err_symbol./(tot_frame_tx * symbol_per_frame) ;
    ber_snr=tot_err_bit./(tot_frame_tx * symbol_per_frame*2);
    figure(1);
   semilogy(0:max_snr,ser_snr,'-o');
    grid
    hold on
    semilogy(0:max_snr,ber_snr,'-*');
    xlabel('SNR');
    ylabel('Error Ratio');
    legend('SER-SNR','BER-SNR');
    title('Ideal CSI');
    hold off