function [Pe]=bpsk_over_awgn(snr_in_db)
E=1;    %Normalize energy
snr=10^(snr_in_db/10);
sgma=E/sqrt(2*snr);  %standard deviation of noise
Num=4000;  % The number of binary data
%generation of binary data
for i=1:Num
    u=rand;
    if(u<=0.5)
        data(i)=0;
    else
        data(i)=1;
    end;
end;
%Detection and calculation BER
error=0;
% The correlator outputs
for i=1:Num
    if(data(i)==1)
        r=E+Normal(sgma);
    else
        r=-E+Normal(sgma);
    end;
% Detection
   if(r>0)
      result=1;
    else
    result=0;
end;
if(result~=data(i))  %error accumlator
    error=error+1;
   end;
end;
Pe=error/Num;   %Calculation BER