QPSK.rar_NOISE_modulator_qam

close all clc clear all SNR_DB=[0:1:12]; sum=1000000; data= randsrc(sum,2,[0 1]); [a1,b1]=find(data(:,1)==0&data(:,2)==0); message(a1)=-1-j; [a2,b2]=find(data(:,1)==0&data(:,2)==1); message(a2)=-1+j; [a3,b3]=find(data(:,1)==1&data(:,2)==0); message(a3)=1-j; [a4,b4]=find(data(:,1)==1&data(:,2)==1); message(a4)=1+j; scatterplot(message) title('B Constellation signal point') A=1; Tb=1; Eb=A*A*Tb; P_signal=Eb/Tb; NO=Eb./(10.^(SNR_DB/10)); P_noise=P_signal*NO; sigma=sqrt(P_noise); for Eb_NO_id=1:length(sigma) noise1=sigma(Eb_NO_id)*randn(1,sum); noise2=sigma(Eb_NO_id)*randn(1,sum); receive=message+noise1+noise2*j; resum=0; total=0; m1=find(angle(receive)<=pi/2&angle(receive)>0); remessage(1,m1)=1+j; redata(m1,1)=1; redata(m1,2)=1; m2= find( angle(receive)>pi/2&angle(receive)<=pi); remessage(1,m2)=-1+j; redata(m2,1)=0; redata(m2,2)=1; m3=find( angle(receive)>-pi&angle(receive)<=-pi/2); remessage(1,m3)=-1-j; redata(m3,1)=0; redata(m3,2)=0; m4=find( angle(receive)>-pi/2&angle(receive)<=0); remessage(1,m4)=1-j; redata(m4,1)=1; redata(m4,2)=0; [resum,ratio1]=symerr(data,redata); pbit(Eb_NO_id)=resum/(sum*2); [total,ratio2]=symerr(message,remessage); pe(Eb_NO_id)=total/sum; end scatterplot(receive) title('C Constellation signal point') Pe=1-(1-1/2*erfc(sqrt(10.^(SNR_DB/10)/2))).^2; Pbit=1/2*erfc(sqrt(10.^(SNR_DB/10)/2)); figure(3) semilogy(SNR_DB,pe,':s',SNR_DB,Pe,'-*',SNR_DB,pbit,'-o',SNR_DB,Pbit,':+') legend('QPSK Simulation BER','QPSK Theoretical BER','QPSK Simulation BER','QPSK Theoretical BER',1) xlabel('SNR/dB') ylabel('Probability P') grid on