基于Matlab的turbo码仿真系统

%logmap译码算法,zhenshu为所选帧包含的bit数 function [l_all,waixinxi]=logmapsuanfa(shuru,g,xianyan,index) zhenshu=length(shuru)/2; [n,k]=size(g); m=k-1; state=2^m; a=zeros(zhenshu+1,state); b=zeros(zhenshu+1,state); [next_out,next_state,last_out,last_state] = wanggersc(g); jidazhi=1e10; a(1,1)=0; a(1,2:state)=-jidazhi*ones(1,state-1); if (index==1) b(zhenshu,1)=0; b(zhenshu,2:state)=-jidazhi*ones(1,state-1); else b(zhenshu,1:state)=zeros(1,state); end %计算a for i=2:zhenshu+1 for j=1:state qiao=-jidazhi*ones(1,state); qiao(last_state(j,1))=-log(1+exp(xianyan(i-1)))-shuru(2*i-3)+shuru(2*i-2)*last_out(j,2); qiao(last_state(j,2))=xianyan(i-1)-log(1+exp(xianyan(i-1)))+shuru(2*i-3)+shuru(2*i-2)*last_out(j,4); if (sum(exp(qiao+a(i-1,:)))<1e-300) a(i,j)=-jidazhi; else a(i,j)=log(sum(exp(qiao+a(i-1,:)))); end end temp(i)=max(a(i,:)); a(i,:)=a(i,:)-temp(i); end %计算b for i=zhenshu-1:-1:1 for j=1:state qiao=-jidazhi*ones(1,state); qiao(next_state(j,1))=-log(1+exp(xianyan(i+1)))-shuru(2*i+1)+shuru(2*i+2)*next_out(j,2); qiao(next_state(j,2))=xianyan(i+1)-log(1+exp(xianyan(i+1)))+shuru(2*i+1)+shuru(2*i+2)*next_out(j,4); if (sum(exp(qiao+b(i+1,:)))<1e-300) b(i,j)=-jidazhi; else b(i,j)=log(sum(exp(qiao+b(i+1,:)))); end end temp(i)=max(b(i,:)); b(i,:)=b(i,:)-temp(i); end %计算l_all for i=1:zhenshu for j=1:state qiao0=-log(1+exp(xianyan(i)))-shuru(2*i-1)+shuru(2*i)*last_out(j,2); qiao1=xianyan(i)-log(1+exp(xianyan(i)))+shuru(2*i-1)+shuru(2*i)*last_out(j,4); temp0(j)=exp(qiao0+a(i,last_state(j,1))+b(i,j)); temp1(j)=exp(qiao1+a(i,last_state(j,2))+b(i,j)); end l_all(i)=log(sum(temp1))-log(sum(temp0)); end for i=1:zhenshu waixinxi(i)=2*shuru(2*i-1); waixinxi(i)=l_all(i)-waixinxi(i)-xianyan(i); end