function [p]=smldPe54(snr_in_dB)
% find 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);               %signal ,standard deviation of noise
N=10000;
% generation of the binary data soure
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+gauss(sgma);
        r1=gauss(sgma);
    else
        r0=gauss(sgma);
        r1=E+gauss(sgma);
    end;
    %detector follows
    if (r0>r1)
        decis=0;
    else
        decis=1;
    end;
    if (decis~=dsource(i))
        numoferr=numoferr+1;
    end;
end;
p=numoferr/N;