ldpc_decode_logforofdm1.m

用Matlab实现的LDPC编码程序

%function [x_hat,success,kk,Le_vector]=ldpc_decode_logforOFDM1(Q,r,sigma2,H)
r=y;
Q=1;
en=10^(3/10);
sigma2=0;%2/(2*4*en/2);

[ii,jj,sH]=find(H);
[M,N]=size(H);
afam=sparse(M,1);
indx=sub2ind(size(H),ii,jj);
%lamta_n0=2*r./sigma2;
lamta_n0=r;
%lamta_n0=1/5*r;
lamta_n=lamta_n0;%*0.8862;
Umn=sparse(M,N);
Umn1=Umn;
success=0;
max_iter=50;
kk=0;
%f=inline('log(1+2./(exp(x)-1))','x');
format long
while ((success==0)&(kk<max_iter)),
  kk=kk+1;
  lamtanmatr=H*spdiags(lamta_n(:),0,N,N);
  aa=Umn-lamtanmatr;
  signaa=sign(aa);sigbb=signaa;sigbb=(sigbb-H)./2;
  sigbb=-2*mod(sum(sigbb'),2)+1;
  sigbbmatr=spdiags(sigbb(:),0,M,M)*H;
  signcc=-sigbbmatr.*signaa;
  aa=abs(aa);
  bb=aa;
  bb1=log(coth((bb(indx)+eps)/2));
  bb=sparse(ii,jj,bb1);
  sumbb=sum(bb');
  sumbbmatr=spdiags(sumbb(:),0,M,M)*H;
  cc=log(coth((sumbbmatr(indx)-bb(indx)+eps)/2));
  cc=sparse(ii,jj,cc);
  Umn1=signcc.*cc;
  lamta_n=lamta_n0+sum(Umn1);
  x_hat=lamta_n;
  %x_hat=(sign(lamta_n)+1)./2;
  %%%%%%%%%% Best Decoded %%%%%%%%%%%%%%%%%%
  checkofH=mod(H*x_hat',2);
  checkofH=sum(checkofH);
  if kk==1;
   checkofH0=checkofH;
   x_hat_bestdecoded=x_hat;
  elseif checkofH<checkofH0,
   x_hat_bestdecoded=x_hat;
   checkofH0=checkofH;
  end;
  if checkofH==0;
     success=1;
     fprintf('during the %d equalization iteration;during the %d decoding iteration,the decoding is success!\n',Q,kk); 
  end;
  Umn=Umn1;
end;
Le_vector=lamta_n;