qpsk.m

仿真了QPSK

clear;
Fd=1;
Fs=3*Fd;
M=4;
for SNR_db=0:10:20
    Eb_N0=10^(SNR_db/10);
    sgma=sqrt(1/(8*Eb_N0));
    x=randint(10,1,M);
    y=dmodce(x,Fd,Fs,'psk',M);
    ynoise=y+sqrt(Fs/Fd)*sgma*(randn(length(y),1)+j*randn(length(y),1));
    z=ddemodce(ynoise,Fd,Fs,'psk',M);
    [numbers,pm(SNR_db/10+1)]=symerr(x,z);
    figure(SNR_db+1);
    hold on;
    for i=0:M-1
        plot(cos(2*pi*i/M),sin(2*pi*i/M),'.','MarkerSize',20);
    end
    plot(ynoise,'+');
    hold off;
end;

SNR_db=0:20;
SNR1_db=0:20;
for n=1:length(SNR_db)
    Eb_N0=10^(SNR_db(n)/10);
    sgma=sqrt(1/(8*Eb_N0));
    x=randint(10000,1,M);
    y=dmodce(x,Fd,Fs,'psk',M);
    ynoise=y+sqrt(Fs/Fd)*sgma*(randn(length(y),1)+j*randn(length(y),1));
    z=ddemodce(ynoise,Fd,Fs,'psk',M);
    [numbers,pm(n)]=symerr(x,z);
end;

for m=1:length(SNR1_db)
    Eb_N0=10^(SNR1_db(m)/10);
    pm_theory(m)=2*Qfunct(sqrt(2*Eb_N0))*(1-1/2*Qfunct(sqrt(2*Eb_N0)));
    pe_theory(m)=pm_theory(m)/log2(M);
end

semilogy(SNR_db,pm,'*',SNR1_db,pm_theory);
xlabel('信噪比(dB)');
ylabel('误符号率');
legend('仿真得到的误符号率','理论符号误码曲线');