ldpc_decode_logforofdm.m

基于LDPC的OFDM系统仿真程序

function [x_hat,success,kk]=ldpc_decode_logforOFDM(r,sigma,H)
[ii,jj,sH]=find(H);
[M,N]=size(H);afam=sparse(M,1);
indx=sub2ind(size(H),ii,jj);
lamta_n0=2*r./sigma/sigma*0.8862;lamta_n=lamta_n0;%*0.8862;
Umn=sparse(M,N);Umn1=Umn;
success=0;max_iter=100;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;bb=log(coth((bb(indx)+eps)/2));
  bb=sparse(ii,jj,bb);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=(sign(lamta_n)+1)./2;
  if rem(H*x_hat',2)==0, 
      success=1;
  end 
  Umn=Umn1;
end;