b2s_logp.m

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function logp_s=b2s_logp(LLR_b,point)

%feature accel on;
bitseq=de2bi(point-1,4,'left-msb');
logp_s=0;
for loop=1:4
    if bitseq(loop)==1,
        if LLR_b(loop)<-10,
            logp_s=logp_s + LLR_b(loop);
        else
            logp_s=logp_s - log(1+exp(-LLR_b(loop)));
        end
    else
        if LLR_b(loop)>10,
            logp_s=logp_s - LLR_b(loop);
        else
            logp_s=logp_s - log(1+exp(LLR_b(loop)));
        end
    end
end