hndiviterbi.zip_viterbi

function [mybit,decoder_output,BER,channel_output,cumulated_metric,survivor_state,y]=viterbi_ber %changdu=input('Please input the length of the code sequence\n\n'); biaozhi=input('please choose the restrict length of the encoder\n3:restrict length=3\n7:restrict length=7\n'); save mybiaozhi biaozhi %mybit=fix(rand(1,changdu)+0.5); % 产生随机信息 %pause mybit=[fix(rand(1,84)) 0 1 1 1 1 1 1 1 1 1 1 1 fix(rand(1,104)) 0 1 0 0 fix(rand(1,12))]; % 卷积编码 if biaozhi==3 G=[1 1 1;1 0 1]; % (2,1,3)生成矩阵 elseif biaozhi==7 G=[1 1 1 1 0 0 1;1 0 1 1 0 1 1]; % (2,1,7)生成矩阵 end k=1; right_channel_output=cnv_encd(mybit); %pause lgth=length(right_channel_output); %xunhuan=input('please input the number of the cycle\n'); %BER=zeros(1,xunhuan); %cumulated_metric_table=zeros(1,xunhuan); %decoder_output_table=zeros(xunhuan,lgth/2-biaozhi+1); %channel_output_table=zeros(xunhuan,lgth); % 模拟信道误码 %for z=1:xunhuan channel=zeros(1,lgth); %p=input('please input the number of the erroe bit\n'); %for z=1:2 %if z==1 %channel_output=right_channel_output; %end %if z==2 %for i=1:444 %channel(i)=1; %end %信道误码率＝1/z,即每循环一次，就有一个信道误码率p %for yz=18:32 % channel(yz)=1; %end %end %channel_output=mod(right_channel_output+channel,2) %end %channel_output=input('please input the erroe code sequence\n'); %channel_output_table(z,:)=channel_output; % 数据转移 channel_output=right_channel_output; n=size(G,1); % n=G的行数 % 检查大小 if rem(size(G,2),k)~=0 error('Size of G and k do not agree') % 存在合理的约束长度 end if rem(size(channel_output,2),n)~=0 error('channel output not of the right size') % 经过信道后，进入译码器前，卷积编码的个数合理 end L=size(G,2)/k; % 约束长度＝寄存器个数+1 number_of_states=2^((L-1)*k); % 状态数 % 产生状态转移矩阵、输出矩阵和输入矩阵 for j=0:number_of_states-1 % 对(2,1,3) j=0,1,2,3 for l=0:2^k-1 % l=0,1 [next_state,memory_contents]=nxt_stat(j,l,L,k); myinput(j+1,next_state+1)=l; branch_output=rem(memory_contents*G',2); % 状态图上根据寄存器状态和input作出的编码 nextstate(j+1,l+1)=next_state; % 生成矩阵，含有十进制表示的下一状态 output(j+1,l+1)=bin2deci(branch_output); % 生成矩阵，含有十进制表示的卷积编码 end end state_metric=zeros(number_of_states,2); % 4行，2列 (初始化) depth_of_trellis=length(channel_output)/n; % 需要译码的个数 设为6 channel_output_matrix=reshape(channel_output,n,depth_of_trellis); % 将经过信道的编码序列转换为以需要译码的个数为行数，以n为列数的矩阵 survivor_state=zeros(number_of_states,depth_of_trellis+1); % 4行，7列 (初始化) % 开始无尾信道输出解码 for i=1:depth_of_trellis-L+1 % i=1,2,3,4 flag=zeros(1,number_of_states); % 1行，4列 (初始化) if i<=L step=2^((L-i)*k); % i=1,2,3 step= 4,2,1 else step=1; % i=4 step=1 end for j=0:step:number_of_states-1 % i=1 j=0;i=2 j=0, 2;i=3,4 j=0,1,2,3 for l=0:2^k-1 % l=0,1 branch_metric=0; % 初始化 binary_output=deci2bin(output(j+1,l+1),n); % 将此时刻十进制的编码结果用二进制表示 for ll=1:n % ll=1,2 branch_metric=branch_metric+metric(channel_output_matrix(ll,i),... binary_output(ll)); % 将此时刻经过信道的编码与理论编码比较，得到分支度量值 end if ((state_metric(nextstate(j+1,l+1)+1,2)>state_metric(j+1,1)... +branch_metric)|flag(nextstate(j+1,l+1)+1)==0) state_metric(nextstate(j+1,l+1)+1,2)=state_metric(j+1,1)+branch_metric; survivor_state(nextstate(j+1,l+1)+1,i+1)=j; flag(nextstate(j+1,l+1)+1)=1; end end end state_metric=state_metric(:,2:-1:1); end % 开始有尾信道输出解码 for i=depth_of_trellis-L+2:depth_of_trellis flag=zeros(1,number_of_states); last_stop=number_of_states/(2^((i-depth_of_trellis+L-2)*k)); for j=0:last_stop-1 branch_metric=0; binary_output=deci2bin(output(j+1,1),n); for ll=1:n branch_metric=branch_metric+metric(channel_output_matrix(ll,i),binary_output(ll)); end if ((state_metric(nextstate(j+1,1)+1,2)>state_metric(j+1,1)... +branch_metric)|flag(nextstate(j+1,1)+1)==0) state_metric(nextstate(j+1,1)+1,2)=state_metric(j+1,1)+branch_metric; survivor_state(nextstate(j+1,1)+1,i+1)=j; flag(nextstate(j+1,1)+1)=1; end end state_metric=state_metric(:,2:-1:1); end % 从最佳路径中产生解码 state_sequence=zeros(1,depth_of_trellis+1); state_sequence(1,depth_of_trellis)=survivor_state(1,depth_of_trellis+1); for i=1:depth_of_trellis state_sequence(1,depth_of_trellis-i+1)=survivor_state((state_sequence(1,depth_of_trellis+2-i)... +1),depth_of_trellis-i+2); end decoder_output_matrix=zeros(k,depth_of_trellis-L+1); for i=1:depth_of_trellis-L+1 dec_output_deci=myinput(state_sequence(1,i)+1,state_sequence(1,i+1)+1); dec_output_bin=deci2bin(dec_output_deci,k); decoder_output_matrix(:,i)=dec_output_bin(k:-1:1)'; end decoder_output=reshape(decoder_output_matrix,1,k*(depth_of_trellis-L+1)); %decoder_output_table(z,:)=decoder_output; %decoder_output_table(z,:)=decoder_output; % 数据转移 cumulated_metric=state_metric(1,1); %cumulated_metric_table(z)=cumulated_metric; % 数据转移 BER=Bit_Error_Rate(mybit,decoder_output); %channel_BER(z)=Bit_Error_Rate(right_channel_output,channel_output); y=mod((decoder_output+mybit),2); %end %----------------------------------------subfunction Bit_Error_Rate------------------------------------------------- function y=Bit_Error_Rate(a,b) y=nnz(mod(a+b,2))/length(a); %-------------------------------------------subfunction cnv_encd---------------------------------------------------- function the_output1=cnv_encd(mybit) % the_output1为完全正确译码，编码输出结果多出2*移位寄存器个数； the_output2为不完全译码，译码结果与编码之前的原始信息