snr=1:1000;
pe=1./2*erfc(sqrt(snr));
pe2=1./2*erfc(sqrt(snr/2));
pe3=1./2*erfc(sqrt(snr/4));
pe4=1./2*erfc(sqrt(snr*(1-P1)/2));
pe5=1./2*erfc(sqrt(snr*(1-P2)/2));



figure(1);
snr=10*log(snr)/log(10);
figure(1);
semilogy(snr,pe,'-rs');
hold on;
semilogy(snr,pe2,'-kd');
semilogy(snr,pe3,'-g+');
semilogy(snr,pe4,'-*');
semilogy(snr,pe5,'-b+');
grid on;
axis([0 20 10e-8 1]);
T=title('BER PLOT(理想)');
set(T,'FontSize',14);
X=xlabel('Eb/N0(in dB)');
set(X,'FontSize',14);
Y=ylabel('Bit Error Rate');
set(Y,'FontSize',14);

snr=1:5:200;
snr=snr/4;
pa=1./2*erfc(sqrt(snr));
pa2=1./2*erfc(sqrt(snr/2));
pa3=1./2*erfc(sqrt(snr/4));
pa4=1./2*erfc(sqrt(snr*(1-P1)/2));
pa5=1./2*erfc(sqrt(snr*(1-P2)/2));


figure(2);
snr=10*log(snr)/log(10);
semilogy(snr,pa,'-rs');
hold on;
semilogy(snr,pa2,'-kd');
semilogy(snr,pa3,'-g+');
semilogy(snr,pa4,'-*');
semilogy(snr,pa5,'-b+');
grid on;
axis([0 20 10e-8 1]);
T=title('BER PLOT(實際)');
set(T,'FontSize',14);
X=xlabel('Eb/N0(in dB)');
set(X,'FontSize',14);
Y=ylabel('Bit Error Rate');
set(Y,'FontSize',14);