QC-LDPC的编译码的matlab误码率仿真-源码

function x_hat = func_Ldpc_dec(z,sigma,H); f1 = 1./(1 + exp(-2*z/sigma^2)); f0 = 1 - f1; [m,n] = size(H); if m>n H = H'; [m,n] = size(H); end if ~issparse(H) [ii,jj,sH] = find(H); H = sparse(ii,jj,sH,m,n); end [ii,jj] = find(H); indx = sub2ind(size(H),ii,jj); q0 = H * spdiags(f0(:),0,n,n); sq0 = full(q0(indx)); sff0 = sq0; q1 = H * spdiags(f1(:),0,n,n); sq1 = full(q1(indx)); sff1 = sq1; k = 0; success = 0; max_iter = 20; while ((success == 0) & (k < max_iter)) k = k+1; sdq = sq0 - sq1; sdq(find(sdq==0)) = 1e-20; dq = sparse(ii,jj,sdq,m,n); Pdq_v = full(real(exp(sum(spfun('log',dq),2)))); Pdq = spdiags(Pdq_v(:),0,m,m) * H; sPdq = full(Pdq(indx)); sr0 = (1+sPdq./sdq)./2; sr0(find(abs(sr0) < 1e-20)) = 1e-20; sr1 = (1-sPdq./sdq)./2; sr1(find(abs(sr1) < 1e-20)) = 1e-20; r0 = sparse(ii,jj,sr0,m,n); r1 = sparse(ii,jj,sr1,m,n); Pr0_v = full(real(exp(sum(spfun('log',r0),1)))); Pr0 = H * spdiags(Pr0_v(:),0,n,n); sPr0 = full(Pr0(indx)); Q0 = full(sum(sparse(ii,jj,sPr0.*sff0,m,n),1))'; sq0 = sPr0.*sff0./sr0; Pr1_v = full(real(exp(sum(spfun('log',r1),1)))); Pr1 = H * spdiags(Pr1_v(:),0,n,n); sPr1 = full(Pr1(indx)); Q1 = full(sum(sparse(ii,jj,sPr1.*sff1,m,n),1))'; sq1 = sPr1.*sff1./sr1; sqq = sq0+sq1; sq0 = sq0./sqq; sq1 = sq1./sqq; QQ = Q0+Q1; Q0 = Q0./QQ; Q1 = Q1./QQ; x_hat = (sign(Q1-Q0)+1)/2; if rem(H*x_hat,2) == 0 success = 1; end end