QPSK_System_BER_Simulation.zip_QPSK_BER，瑞利_QPSK调制 BER_qpsk rayle

function [pb,ps]=cm_sm32(snr_in_dB) % [pb,ps]=cm_sm32(snr_in_dB) % CM_SM3 finds the probability of bit error and symbol error for % the given value of snr_in_dB, signal to noise ratio in dB. N=10000; E=1; % energy per symbol snr=10^(snr_in_dB/10); % signal to noise ratio sgma=sqrt(E/snr)/2; % noise variance s00=[1 0]; s01=[0 1]; s11=[-1 0]; s10=[0 -1]; % signal mapping % generation of the data source for i=1:N, temp=rand; % a uniform random variable between 0 and 1 if (temp<0.25), % with probability 1/4, source output is "00" dsource1(i)=0; dsource2(i)=0; elseif (temp<0.5), % with probability 1/4, source output is "01" dsource1(i)=0; dsource2(i)=1; elseif (temp<0.75), % with probability 1/4, source output is "10" dsource1(i)=1; dsource2(i)=0; else % with probability 1/4, source output is "11" dsource1(i)=1; dsource2(i)=1; end; end; % detection and the probability of error calculation numofsymbolerror=0; numofbiterror=0; for i=1:N, % the received signal at the detection, for the ith symbol,is: n=sgma*randn(1,2); % 2 normal distributed r.v with 0, variance 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; % The correlation metrics are computed below c00=dot(r,s00); c01=dot(r,s01); c10=dot(r,s10); c11=dot(r,s11); % The decision on the ith symbol is made next 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; % Increment the error counter, if the decision is not correct 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; % since there are totally N symbols pb=numofbiterror/(2*N); % since 2N bits are transmitted