polarcode_SCLscheme.rar

%%%%这个函数用SCL的译码算法进行译码 %%y0是从信道来的接收向量 %%z用来指示信息位和固定位的位置 %%no_of_L是保留的路径个数 只可以取2的幂次 比如4 8 16 %%ccitt是CRC校验多项式 %%layer_number是把码树分的层数 function y=SCL_CRC_decoder(y0,z,no_of_L,ccitt,layer_number) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%初始化 [L xx]=size(y0); %%z用来指示自由位和固定位的位置，y0是从信道接收的列向量，L是码长 Lo=no_of_L; %%Lo是SCL中L的值 Flag=log2(Lo); %%Flag用于指示Lo条路径的选取方法的切换 u_matrix=zeros(Lo,L+1); %%是一个Lo*（L+1）的矩阵，每一行对应一串码字，最后一位是码串的概率 u_temp=zeros(2*Lo,2); %%存放2Lo个码字串的判断位置，用于选出Lo个码字串的临时矩阵 u_temp(1:2:2*Lo,1)=ones(Lo,1) reserve_all=travel(Lo) flag=0; %%表示当前还没有遇到第一个信息位 free_position=find(z==1); %%这个矩阵用来存放信息位的位置索引 free_length=length(free_position)%%信息位的长度 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%% SCL译码 for i=1:L %%i表示已经判决了（i-1）个bit % i % u_matrix %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%矩阵初始化 % if i==1 %%此时是初始化u_matrix 既然码率不能达到1，那么第一位必然是固定位 % u_matrix(:,1)=zeros(Lo,1); %%第一位全部赋0 % %u_matrix(:,L+1)=ones(Lo,1); %%概率位置全部赋1 % continue; % end %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%i表示当前要判断码字中的第i位 flag表示要判断当前的第flag个信息 if z(i)==0 %%对于固定位置 在该位置为0的概率赋值1 u_matrix(:,i)=zeros(Lo,1); else %%对于自由位 要分两种情况 1.需要全部保留路径 2.选取最优路径 flag=flag+1; %%此时的flag表示正在判断第几个信息位 % flag if flag<=Flag %%此时要保留所有路径 并算概率 u_matrix(:,i)=reserve_all(:,flag); if flag==Flag for j=1:Lo %%j循环表示遍历Lo个码串 u_matrix(j,L+1)=channel_transfer(L,i,y0,u_matrix(j,1:i-1),u_matrix(j,i)); end end % u_matrix else %%此时要选取最优路径 for j=1:Lo %%j循环表示遍历Lo个码串 u_temp(2*j-1,2)=channel_transfer(L,i,y0,u_matrix(j,1:i-1),1); u_temp(2*j,2) =channel_transfer(L,i,y0,u_matrix(j,1:i-1),0); %%上两行计算了在当前条件下分别下一位取0和1的总路径概率 [vals,inds] =sort(u_temp(:,2),'descend'); %%将概率值降序排列 temp=[]; for k=1:Lo %%%这个循坏用于从2Lo个概率值中选取最优 if mod(inds(k),2)==1 %%奇数索引值表示最后一位是1，tempcode最后一位是该路径的概率 tempcode=[u_matrix((inds(k)+1)/2,1:i-1),1,vals(k)]; temp=[temp;tempcode]; else %%偶数索引表示最后一位是0 ，tempcode最后一位是该路径的概率 tempcode=[u_matrix(inds(k)/2,1:i-1),0,vals(k)]; temp=[temp;tempcode]; end end %%end of k_cycle end %%end of j_cycle % temp u_matrix(:,1:i)=temp(:,1:i); u_matrix(:,L+1)=temp(:,i+1); end %%end of if if mod(flag,free_length./layer_number)==0 %%当判断的当前位置正好是层的边界时 进行CRC校验 并选择最大概率的输出 no_of_rank=flag./(free_length./layer_number); %%no_of_rank用来存放当前的层数 for ii=1:Lo [values,index]=sort(u_matrix(:,L+1),'descend'); err=cyclic_redundancy_decode( u_matrix(index(ii),free_position((no_of_rank-1).*free_length./layer_number+1:no_of_rank.*free_length./layer_number)),ccitt ); if err == 0 %%校验式通过CRC for jj=1:Lo u_matrix(jj,free_position((no_of_rank-1).*free_length./layer_number+1:no_of_rank.*free_length./layer_number))=u_matrix(index(ii),free_position((no_of_rank-1).*free_length./layer_number+1:no_of_rank.*free_length./layer_number)); end u_matrix(:,L+1)=ones(Lo,1); break; else %%此时err=1 码式没有通过CRC continue; end end end end %%end of if end %%end of i_cycle %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%最后从Lo条路径中选取最大的一条输出 y=u_matrix(1,1:L)'; end