qpsk-mimo.m

根据TD-SCDMA系统的特点

close all;
clear all;
randn('state',sum(100*clock)); %reset the randn generator


A=1;
Es=A*A;

myCst=A*[1,-1]; %the constellation
myMap=[1,0];

Eb=2*Es;
minTestLength=100000; % test length should at least reach this number
maxTestLength=100000000; %test stops at this number 

index=1;
for EbN0=0:1:15 %EbN0 in dB

    N0=Eb*10^(-EbN0/10);
    noiseRoot=sqrt(N0/2);
    errorCount=0;
    testCount=0;
    while(1)
        % Generate the Rayleigh fading channel
        h0=(randn(1)+j*randn(1))*sqrt(0.5);
        h1=(randn(1)+j*randn(1))*sqrt(0.5);
        h2=(randn(1)+j*randn(1))*sqrt(0.5);
        h3=(randn(1)+j*randn(1))*sqrt(0.5);

        %Noise generator
        n0=(randn(1)+j*randn(1))*noiseRoot;
        n1=(randn(1)+j*randn(1))*noiseRoot;
        n2=(randn(1)+j*randn(1))*noiseRoot;
        n3=(randn(1)+j*randn(1))*noiseRoot;

        %Binary source 
        src=randn(2,2)>0; %binary source with equal probability

        x=A*(2*src-1); %'0' maps to -A, '1' maps to A
        
        for i=1:2 
        %Simulate the MIMO channel with noise
        S0=x(i,1);
        S1=x(i,2);
        r0=h0*S0+h1*S1+n0;
        r1=-h0*conj(S1)+h1*conj(S0)+n1;
        r2=h2*S0+h3*S1+n2;
        r3=-h2*conj(S1)+h3*conj(S0)+n3;

        %MRC receiver

        S0_MRC=conj(h0)*r0+h1*conj(r1)+conj(h2)*r2+h3*conj(r3);
        S1_MRC=conj(h1)*r0-h0*conj(r1)+conj(h3)*r2-h2*conj(r3);

        %Decision
        myDist0=(S0_MRC-myCst).*conj(S0_MRC-myCst);
        myDist1=(S1_MRC-myCst).*conj(S1_MRC-myCst);
        [temp0,myIndex0]=min(myDist0);
        [temp1,myIndex1]=min(myDist1);

        dst=[myMap(myIndex0),myMap(myIndex1)];
        err=xor(src(i,:),dst);
        errorCount=errorCount+sum(err);
        testCount=testCount+2;
    end
        if(testCount<minTestLength)
            continue;
        end
        tempBER=errorCount/testCount;

         %test if the test length is large enough
        if(tempBER>0)
            thresholdTestLength=100/(tempBER);
        else
            thresholdTestLength=maxTestLength;
        end
        
        %Stop current EbN0 test when the test threshold is reached
        if(testCount>=thresholdTestLength)
            myTestLength(index)=testCount;
            Es=Eb/2;
            myEsN0(index)=10*log10(Es/N0)
            myEbN0(index)=EbN0
            myBER(index)=tempBER
            index=index+1;
            break;
        end
    end
end

%Draw curves for the results,Eb/N0
figure(1)
semilogy(myEbN0,myBER,'*-');
xlabel('Eb/N0 in dB');
ylabel('bit error rate');
grid

%Draw curves for the results, Es/N0
figure(2)
semilogy(myEsN0,myBER,'+-');
xlabel('Es/N0 in dB');
ylabel('bit error rate');
grid