[pb,ps]=cmsm(snrdb)

function [pb,ps]=cmsm(snrdb)
N=10000;
E=1;
snr=10^(snrdb/10);
sgma=sqrt(E/snr)/2;
s00=[1 0];
s01=[0 1];
s11=[-1 0];
s10=[0 -1];
for i=1:N,
temp=rand;
if(temp<0.25)
    dsource1(i)=0;
dsource2(i)=0;
elseif(temp<0.5)
dsource1(i)=0;
dsource2(i)=1;
elseif(temp<0.75)
dsource1(i)=1;
dsource2(i)=0;
else
dsource1(i)=1;
dsource2(i)=1;
end;
end;
numofsymbolerror=0;
numofbiterror=0;
for i=1:N
n(1)=normrnd(0,sgma);
n(2)=normrnd(0,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;
c00=dot(r,s00);
c01=dot(r,s01);
c10=dot(r,s10);
c11=dot(r,s11);
cmax=max([c00 c01 c10 c11]);
if(c00==cmax)
decis1=0;decis2=0;
elseif(c01==cmax)
decis1=0;decis2=1;
elseif(c10==cmax)
decis1=1;decis2=0;
else
decis1=1;decis2=1;
end;
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;
pb=numofbiterror/(2*N);
title('Probability of Error Performance')
xlabel('SNR in db')
ylabel('probability of error')