function [BM]=BranchMetric0(t,ps,ns,PS,NS,OP,La,LEI)

N=length(PS);
for k=1:N
    if(ps==PS(k))
        i=k;
        break;
    end
end

if(ns==NS(i,1))
    BM=exp(-0.5*(La+sum(LEI(t,:))));
elseif(ns==NS(i,2))
    BM=exp(0.5*(La+sum(LEI(t,:))));
else
    BM=0;
end