qam64decode_new.m

由4个.m文件组成

%64QAM demodulation
%use the way of Logarithm of Likelihood Ratio (LLR)
%revSymbol is the symbol to be decisioned
%revSymbol is a line vector
%qam_sig is the decisioned complex QAM signal
%suppose that rho=1;
function [qam_sig]=QAM64decode_new(revSymbol)
qam_sig=[];
k=length(revSymbol);
for i1=1:k,
    xk=real(revSymbol(i1));
    yk=imag(revSymbol(i1));
    
%decition for the first bit
    m=[-1 -3 -5 -7 1 3 5 7];
    u=xk;
    w1=LLR(u,m);
    if w1>=0
        c1=1;
    else
        c1=0;
    end
    
%decition for the second bit    
    m=[3 1 -1 -3 7 5 -5 -7];
    u=xk;
    w2=LLR(u,m);
    if w2>0
        c2=1;
    else
        c2=0;
    end
    
%decition for the third bit    
    m=[5 3 -3 -5 7 1 -1 -7];
    u=xk;
    w3=LLR(u,m);
    if w3>=0
        c3=1;
    else
        c3=0;
    end

%decition for the forth bit    
    m=[-7 -5 -3 -1 7 5 3 1];
    u=yk;
    w4=LLR(u,m);
    if w4>0
        c4=1;
    else
        c4=0;
    end
    
%decition for the fifth bit
    m=[-3 -1 1 3 -7 -5 5 7];
    u=yk;
    w5=LLR(u,m);
    if w5>0
        c5=1;
    else
        c5=0;
    end
    
%decition for the sixth bit
    m=[-5 -3 3 5 -7 -1 1 7];
    u=yk;
    w6=LLR(u,m);
    if w6>0
        c6=1;
    else
        c6=0;
    end
    
    qam_sig1=[c1 c2 c3 c4 c5 c6];
    qam_sig=[qam_sig qam_sig1];  
end

%------Logarithm of Likelihood Ratio (LLR)------
function b=LLR(u,m)
    for n=1:8
        a(n)=exp(-((u+m(n))^2)/2);  
    end
    b=log((a(1)+a(2)+a(3)+a(4))/(a(5)+a(6)+a(7)+a(8)));