ldpc_decode_log.m

这是一个关于低密度检验码的很好的matlab程序

function [uhat,vhat]=ldpc_decode_log(rx_waveform,No,amp,h,rearranged_cols)

%global H;

[M,N]=size(h);
L=zeros(1,N);
vhat(1,1:N)=0;
zero(1,1:M)=0;
Lq=+h;
Lr=+h;
%%%%%% Initialization %%%%%%%%%
sigma2=No/2;
L=2.*amp.*rx_waveform./sigma2;
for i=1:M
    L1(i,:)=L;
end
Lq=Lq.*L1;

%%%%%% Iterations:100 %%%%%%
for iteration=1:100
    %%%%%%%%%%% begin horizontal step %%%%%%%%%%%%%%%%%%%%%%
    for j=1:M
        bit=find(h(j,:)~=0);
        for i=1:length(bit)
            tem=bit(find(bit~=bit(i)));
            alfa=prod(sign(Lq(j,tem)));
            beta=-log(tanh(sum(-log(tanh(abs(Lq(j,tem))./2)))/2));
            Lr(j,bit(i))=alfa.*beta;
        end
    end
    %%%%%%%%%%%%%% end horizontal step %%%%%%%%%%%%%%%%%%%%%%%%
    
    %%%%%%%%%%%%%%% begin vertical step %%%%%%%%%%%%%%%%%%%
    for i=1:N
        check=find(h(:,1)==1);
        for j=1:length(check)
            tem=check(find(check~=check(j)));
            Lq(check(j),i)=L(i)+sum(Lr(tem,i));
        end
    end
    %%%%%%%%%%%%%%%%%%% end vertical step %%%%%%%%%%%%%%%%%%%
    
    %%%%%%%%%%%%%%%%%%% tentative decoding %%%%%%%%%%%%%%%%%%%
    LQ=L;
    for i=1:N
        check=find(h(:,i)~=0);
        LQ(i)=LQ(i)+sum(Lr(check,i));
        if LQ(i)>0
            vhat(i)=1;
        end
    end
    
    %%%%%%%%%%%%%%%%%%% stop if vhat*H'=0 %%%%%%%%%%%%%%%%%%%
    if mul_GF2(vhat,h')==zero
        break;
    end
end

uhat = extract_mesg(vhat,rearranged_cols);