cm_sm41.m

matlab通信仿真

function [p]=cm_sm41(snr_in_dB)
% This function finds the probability of error for the given value of
% snr_in_dB, SNR in dB

N=20000;
d=1;                   %min. distance between symbols
Eav=10*d^2;       % energy per symbol
snr=10^(snr_in_dB/10);       % SNR per bit (given)
sgma=sqrt(Eav/(8*snr));       % noise variance
M=16;

% generation of the data source 
for i=1:N
    temp=rand;
    dsource(i)=1+floor(M*temp);
end

% mapping to the signal constellation 
mapping=[-3*d  3*d;
                -d 3*d;
                d   3*d;
                3*d 3*d;
                -3*d  d;
                -d  d;
                d  d;
                3*d  d;
                -3*d  -d;
                -d  -d;
                d  -d;
                3*d  -d;
                -3*d  -3*d;
                -d  -3*d;
                d  -3*d;
                3*d   -3*d];
    
   for i=1:N
       qam_sig(i,:)=mapping(dsource(i),:);
   end
   
   % Received signal
   for i=1:N
       [n(1) n(2)]=gngauss(sgma);
       r(i,:)=qam_sig(i,:)+n;
   end
   
   scatterplot(r);
   %detection and error probability calculation
   numoferr=0;
   for i=1:N
       %metric computation
       for j=1:M
           metrics(j)=(r(i,1)-mapping(j,1))^2+(r(i,2)-mapping(j,2))^2;
       end
       [min_metric decis]=min(metrics);
       if (decis~=dsource(i))
           numoferr=numoferr+1;
       end
   end
   
   p=numoferr/N;