卷积编码和viterbi译码，调制方式为qpsk的matlab程序

%硬判决 Viterbi 译码 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %当输入rcvd卷积码编码序列后，经过biterbi译码，输出dec_op %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% function [dec_op]=viterbidec(rcvd) %Concatenate two consecutive bits of recieved encoded sequence to %构造标记 input=[]; for j=1:2:length(rcvd) input=[ input (rcvd(j))* 2 + (rcvd(j+1))]; end %数组初始化 op_table=[00 00 11; 01 11 00; 10 10 01; 11 01 10]; %输出数组 ns_table=[0 0 2; 1 0 2; 2 1 3; 3 1 3]; %下一状态数组 transition_table=[0 1 1 55; 0 0 1 1; 55 0 55 1; 55 0 55 1]; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 数组更新部分 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% st_hist(1:4, 1:17)=55; %历史状态数组 aem=zeros(4, 17); %累计路径长度数组 ssq=zeros(1, 17); %构造连续状态数组 lim=length(input); %时钟循环数量 for (t=0:1:lim) %时钟循环 if(t==0) st_hist(1,1)=0; %开始状态为00 else temp_state=[];%存储中间状态的数组 temp_metric=[];%存储可能的状态的长度的数组 temp_parent=[];%存储上一状态的数组 for (i=1:1:4) in=input(t); if(st_hist(i, t)==55) %如果是无效状态，无变化 else ns_a=ns_table(i, 2)+1; %下一个状态 state-1 ns_b=ns_table(i, 3)+1; %下一个状态 state-2 op_a=op_table(i, 2); %下一个输出 output-1 op_b=op_table(i, 3); %下一个输出 output-2 cs=i-1; %当前状态 M_a=hamm_dist(in, op_a); %对ns_a各个分支进行度量 M_b=hamm_dist(in, op_b); %对ns_b各个分支进行度量 indicator=0; %指示多余状态的标记 for k=1:1:length(temp_state) %检查下一个多余的状态 %如果下一个可能的状态 state-1是多余的 if(temp_state(1,k)==ns_a) indicator=1; %ADD-COMPARE-SELECT Operation %em_c: 当前状态的度量长度 %em_r: 多余状态的度量 em_c=M_a + aem(i,t); em_r=temp_metric(1,k) + aem(temp_parent(1, k)+1,t); if( em_c< em_r)%比较连个路径的长度 st_hist(ns_a,t+1)=cs;%选择长度小的路径 temp_metric(1,k)=M_a; temp_parent(1,k)=cs; end end %如果下一个可能的状态state-2是多余的 if(temp_state(1,k)==ns_b) indicator=1; em_c=M_b + aem(i,t); em_r=temp_metric(1,k) + aem(temp_parent(1, k)+1,t); if( em_c < em_r)%比较两个分支长度 st_hist(ns_b,t+1)=cs;%选择长度小的路径 temp_metric(1,k)=M_b; temp_parent(1,k)=cs; end end end %如果两可能的状态都非多余 if(indicator~=1) %更新历史状态组 st_hist(ns_a,t+1)=cs; st_hist(ns_b,t+1)=cs; %更新中间矢量 temp_parent=[temp_parent cs cs]; temp_state=[temp_state ns_a ns_b]; temp_metric=[temp_metric M_a, M_b]; end %打印中间变量 temp_parent; temp_state; temp_metric; end end %更新所有路径的累计长度 %现在的瞬时时刻 't' for h=1:1:length(temp_state) xx1=temp_state(1, h); xx2=temp_parent(1, h)+1; aem(xx1, t+1)=temp_metric(1, h) + aem(xx2, t); end end end %结束循环 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 路径反馈部分 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% for(t=0:1:lim) slm=min(aem(:, t+1)); slm_loc=find( aem(:, t+1)==slm ); sseq(t+1)=slm_loc(1)-1; end dec_op=[]; for p=1:1:length(sseq)-1 dec_op=[dec_op, transition_table((sseq(p)+1), (sseq(p+1)+1))]; end