viterbi软判决硬判决译码算法

%硬判决 function decoder_output=viterbi_hard(y,L) global G; n=size(G,1); K=size(G,2); number_of_states=2^(K-1); %------------------------------------------------ %-------------生成各分支的输出-------------------- %------------------------------------------------ for j=0:number_of_states-1 for t=0:1 [next_state,memory_contents]=next_state_fun(j,t,K); input(j+1,next_state+1)=t; branch_output=rem(memory_contents*G',2); nextstate(j+1,t+1)=next_state; output(j+1,t+1)=bin2deci(branch_output); end end %------------------------------------------------ metric_of_states=zeros(1,number_of_states); %各状态的度量metric metric_of_states_c=zeros(number_of_states,2); %各状态两个输入的度量 length_seq=length(y)/n; %符号个数 decoder_output=zeros(1,length_seq-K+1); %解码输出 channel_output_matrix=reshape(y,n,length_seq); %将解调输出的比特按符号排列 survivor_state=zeros(number_of_states,length_seq+1); %留存路径 input_of_state=zeros(number_of_states,length_seq+1,2); %汇聚到各状态的分支对应的输入 state_sequence=zeros(1,length_seq+1); count=zeros(1,number_of_states); for i=1:length_seq-K+1 %------------------------------------------------ for j=0:number_of_states-1 for t=0:1 binary_output=deci2bin(output(j+1,t+1),n); %将各分支的输出转换为2进制 branch_metric=Hamming_dis(channel_output_matrix(:,i)',binary_output); %计算分支度量 count(nextstate(j+1,t+1)+1)=count(nextstate(j+1,t+1)+1)+1; metric_of_states_c(nextstate(j+1,t+1)+1,count(nextstate(j+1,t+1)+1))=metric_of_states(j+1)+branch_metric; %计算累积度量（加） input_of_state(nextstate(j+1,t+1)+1,:,count(nextstate(j+1,t+1)+1))=survivor_state(j+1,:); %该分支所在路径的对应的输入 input_of_state(nextstate(j+1,t+1)+1,i,count(nextstate(j+1,t+1)+1))=t; end; end; %----------------比较汇聚到同一状态的两条路径，选取距离较小的----------------- for j=0:number_of_states-1 if metric_of_states_c(j+1,1)>=metric_of_states_c(j+1,2) metric_of_states(j+1)=metric_of_states_c(j+1,2); survivor_state(j+1,:)=input_of_state(j+1,:,2); else metric_of_states(j+1)=metric_of_states_c(j+1,1); survivor_state(j+1,:)=input_of_state(j+1,:,1); end; end; count=zeros(1,number_of_states); %--------------------------截短输出------------------------------------ if i>L [min_metric,location]=min(metric_of_states); decoder_output(i-L)=survivor_state(location,i-L); end; end %---------------------最后L个比特译码输出-------------------------------- [min_metric,location]=min(metric_of_states); decoder_output(length_seq-K+1-L+1:length_seq-K+1)=survivor_state(location,length_seq-K+1-L+1:length_seq-K+1); % =========================================================