qpsk.m

QPSK调制与解调

SNRindB1=0:2:10;
SNRindB2=0:0.1:10;
for i=1:length(SNRindB1),
    [pb,ps]=snr2p(SNRindgB1(i));
    simu_bit_err_prb(i)=pb;
    simu_symbol_err_prb(i)=ps;
end;
for i=1:length(SNRindB2),
    SNR=exp(SNRindB2(i)*log(10)/10);
    theo_err_prb(i)=Qfunct(2*SNR);
end;
semilogy(SNRindB1,simu_biit_err_prb,'*');
hold
semilogy(SNRindB1,simu_symbol_err_prb,'o');
semilogy(SNRindB2,theo_err_prb);
xlabel('Eb/NO(db)');
ylabel('误码率');
legend('仿真比特误码率','仿真符号误码率','理论比特误码率');
function[pb,ps]=snr2p(snr_in_db);
N=10000;
snr=10^(snr_in_dB/10);
sgma=sqrt(Es/(4*snr));
s00=[1 0];
s01=[0 1];
s11=[-1 0];
s10=[0 -1];
for i=1:N,
    temp=rand;
    if (temp<0.25),
        dsource1(i)=0;
        dsource2(i)=0;
    elseif (temp<0.5),
       dsource1(i)=0;
        dsource2(i)=1;
        elseif (temp<0.75),
                dsource1(i)=1;
        dsource2(i)=0;
    else
                dsource1(i)=1;
        dsource2(i)=1;
    end;
end;
numofsymolerror=0;
numofbiterror=0;
for i=1:N,
    n(1)=gausamp(sgma);
    n(2)=gausamp(sgma);
    if((dsource1(i)==0)&(dsource2(i)==0));
        r=s00+n;
    elseif ((dsource1(i)==0)&(dsource2(i)==1));
        r=s01+n;
        elseif ((dsource1(i)==1)&(dsource2(i)==0));
            r=s10+n;
    else
        r=s11+n;
    end;
    c00=dot(r,s00);
    c01=dot(r,s01);
    c10=dot(r,s10);
    c11=dot(r,s11);
    c_max=max([c00 c01 c10 c11]);
    if (c00==c_max),
        decis1=0;decis2=0;
    elseif (c01==c_max),
         decis1=0;decis2=1;
    elseif (c10==c_max),
        decis1=1;decis2=0;
    else
        decis1=1;decis2=1;
    end;
    symbolerror=0;
    if(decis1~=dsource1(i)),
        numofbiterror=numofbiterror+1;
        symbolerror=1;
    end;
    if (decis2~=dsource2(i)),
        numofbiterror=numofbiterror+1;
        symbolerror=1;
    end;
    if (symbolerror==1),
        numofsymbolerror=numofsymbolerror+1;
    end;
end;
ps=numofsymbolerror/N;
pb=numofbiterror/(2*N);