smldpe54.m

contemporarycommunicatonsystem－using MATLAB经典书目源程序！

function [p]=smldPe54(snr_in_dB)
% [p]=smldPe54(snr_in_dB)
%		SMLDPE54  finds the probability of error for the given
%   		snr_in_dB, signal to noise ratio in dB.
E=1;
SNR=exp(snr_in_dB*log(10)/10);	   	% signal to noise ratio
sgma=E/sqrt(2*SNR);		   	% sigma, standard deviation of noise
N=10000;
% generation of the binary data source
for i=1:N,
  temp=rand;   	      			% a uniform random variable over (0,1)
  if (temp<0.5),
    dsource(i)=0;   	      		% with probability 1/2, source output is 0
  else
    dsource(i)=1;	      		% with probability 1/2, source output is 1
  end
end;
% detection, and probability of error calculation 
numoferr=0;
for i=1:N,
  % matched filter outputs
  if (dsource(i)==0),
    r0=E+gngauss(sgma);
    r1=gngauss(sgma);	      		% if the source output is "0"
  else
    r0=gngauss(sgma);
    r1=E+gngauss(sgma);     		% if the source output is "1"
  end;
  % detector follows
  if (r0>r1),
    decis=0;		      		% decision is "0" 
  else
    decis=1;		      		% decision is "1" 
  end;
  if (decis~=dsource(i)),    		% if it is an error, increase the error counter
    numoferr=numoferr+1;
  end;
end;
p=numoferr/N;	  	      		% probability of error estimate