1、精選優質文檔-傾情為你奉上1、卷積碼編碼function output=cnv_encd(input)%output=cnv_encd(g,k0,input) 卷積碼編碼函數%g 生成矩陣%k0 輸入碼長%input 輸入信源序列%output 輸出卷積編碼序列g=1 1 1;1 0 1;編碼矩陣k0=1;input=1 1 0 1;if rem(length(input),k0)0 input=input,zeros(size(1:k0-rem(length(input),k0);endn=length(input)/k0;if rem(size(g,2),k0)0 error(Error,

2、g is not of the right size.)endli=size(g,2)/k0;n0=size(g,1);u=zeros(size(1:(li-1)*k0),input,zeros(size(1:(li-1)*k0);u1=u(li*k0:-1:1);for i=1:n+li-2 u1=u1,u(i+li)*k0:-1:i*k0+1);enduu=reshape(u1,li*k0,n+li-1);output=reshape(rem(g*uu,2),1,n0*(n+li-1);2、Viterbi譯碼程序1）function y=bin2deci(x)l=length(x);y=(

3、l-1:-1:0);y=2.y;y=x*y;2）function y=deci2bin(x,l)y=zeros(1,l);i=1;while x=0 & i=l y(i)=rem(x,2); x=(x-y(i)/2; i=i+1;endy=y(l:-1:1);3）function distance=metric(x,y)if x=y distance=0;else distance=1;end4）function next_state,memory_contents=nxt_stat(current_state,input,L,k)binary_state=deci2bin(current_s

4、tate,k*(L-1);binary_input=deci2bin(input,k);next_state_binary=binary_input,binary_state(1:(L-2)*k);next_state=bin2deci(next_state_binary);memory_contents=binary_input,binary_state;5）function decoder_output,survivor_state,cumulated_metric=viterbi(channel,snr_db)G=1 1 1;1 0 1; % G 卷積編碼矩陣，如（2,1,3)卷積碼生成

5、矩陣1 1 1;1 0 1,可以根據自己的需要輸入編碼矩陣k=1; % k 信息源輸入端口數 k=1channel=1 1 0 1 0 1 0 0 1 0 1 1 ; %信源編碼snr_db=6;%信噪比，可以通過調節信噪比大小觀察viterbi譯碼的性能%bpsk調制channel_output=bpsk(channel,snr_db);%調用bpsk函數,得到信道編碼n=size(G,1); % n 編碼輸出端口數量,(2,1,3)中n=2if rem(size(G,2),k)=0 %當G列數不是k的整數倍時 error(Size of G and k do not agree) %發出出

6、錯信息endif rem(size(channel_output,2),n)=0 %當輸出量元素個數不是輸出端口的整數倍時 error(channel output not of the right size)endN=size(G,2)/k; %得出移位數，即寄存器的個數M=2k;number_of_states=2(k*(N-1); %狀態數for j=0:number_of_states-1 %j表示當前寄存器組的狀態因為狀態是從零 %開始的,所以循環從0到number_of_states-1 for m=0:M-1 %m為從k個輸入端的信號組成的狀態，總的狀 %態數為2k，所以循環從0

7、到2k-1 %nxt_stat完成從當前的狀態和輸入的矢量得出下寄存器組的一個狀態 next_state,memory_contents=nxt_stat(j,m,N,k);%調用nxt_stat函數 input(j+1,next_state+1)=m; branch_output=rem(memory_contents*G,2); nextstate(j+1,m+1)=next_state; output(j+1,m+1)=bin2deci(branch_output); endend%state_metric數組用于記錄譯碼過程在每狀態時的漢明距離%state_metric大小為numbe

8、r_of_states 2，（:,1）當前%狀態位置的漢明距離，為確定值，而（:,2）為當前狀態加輸入%得到的下一個狀態漢明距離，為臨時值state_metric=zeros(number_of_states,2);depth_of_trellis=length(channel_output)/n;channel_output_matrix=reshape(channel_output,n,depth_of_trellis);survivor_state=zeros(number_of_states,depth_of_trellis+1);for i=1:depth_of_trellis-N+

9、1 flag=zeros(1,number_of_states); if(istate_metric(j+1,1)+branch_metric) | flag(nextstate(j+1,m+1)+1)=0 ) state_metric(nextstate(j+1,m+1)+1,2)=state_metric(j+1,1)+branch_metric; survivor_state(nextstate(j+1,m+1)+1,i+1)=j; flag(nextstate(j+1,m+1)+1)=1; end end end state_metric=state_metric(:,2:-1:1);

10、endfor i=depth_of_trellis-N+2:depth_of_trellis flag=zeros(1,number_of_states); % 狀態數從number_of_statesnumber_of_states/2.21 %程序說明同上，只不過輸入矢量只為0 last_stop=number_of_states/(2(k*(i-depth_of_trellis+N-2); for j=0:last_stop-1 branch_metric=0; binary_output=deci2bin(output(j+1,1),n); for ll=1:n branch_metr

11、ic=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(nex

12、tstate(j+1,1)+1)=1; end end state_metric=state_metric(:,2:-1:1);end%從最佳路徑中產生解碼%譯碼過程可從數組survivor_state的最后一個位置向前逐級譯碼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)=survivo

13、r_state(state_sequence(1,depth_of_trellis+2-i)+1),depth_of_trellis-i+2);enddecoder_output_matrix=zeros(k,depth_of_trellis-N+1);for i=1:depth_of_trellis-N+1 %根據數組input的定義來得出從當前狀態到下一個狀態的輸入信號矢量 dec_output_deci=input(state_sequence(1,i)+1,state_sequence(1,i+1)+1); dec_output_bin=deci2bin(dec_output_deci

14、,k); %將一次譯碼存入譯碼輸出矩陣decoder_output_matrix相應的位置 decoder_output_matrix(:,i)=dec_output_bin(k:-1:1);enddecoder_output=reshape(decoder_output_matrix,1,k*(depth_of_trellis-N+1);cumulated_metric=state_metric(1,1);3、卷積碼譯碼誤碼性能分析clear all;clc;cycl = 50;snr_db = 0:1:10;% 輸入信息msg = randint(1,1024);ber0 = zeros(

15、cycl,length(snr_db);ber1 = zeros(cycl,length(snr_db);ber2 = zeros(cycl,length(snr_db);% Trellisestrel = poly2trellis(3,5 7); %Define trellis for rate 1/2 code.for n = 1:cyclfor x = 1:length(snr_db)% Code wordscode = convenc(msg,trel); % Encode.% Interleaverstate = 20;inter = randintrlv(code,state);%

16、 BPSK 調制s0 = sign(msg - 0.5); s1 = sign(inter-0.5); s2 = sign(code-0.5);% AWGN Channeladd_noise0=awgn(s0,snr_db(x),measured);add_noise1=awgn(s1,snr_db(x),measured);add_noise2=awgn(s2,snr_db(x),measured);% Deinterleaver with noise for soft decodingdeinter_noise = randdeintrlv(add_noise1,state);% 解調r_

17、0 = 0.5*sign(add_noise0) + 0.5;r_1 = 0.5*sign(add_noise1) + 0.5; r_2 = 0.5*sign(add_noise2) + 0.5; % Deinterleaverdeinter_1 = randdeintrlv(r_1,state);% Traceback lengthtblen = 5;% vitdec 硬判決decoded1 = vitdec(deinter_1,trel,tblen,cont,hard);% vitdec 軟判決y,qcode = quantiz(deinter_noise,-.75 -.5 -.25 0 .25 .5 .75,7:-1:0);decoded2 = vitdec(qcode,trel,tblen,cont,soft,3);% 比較誤碼率num0,rat0 = biterr(r_0,msg);num1,rat1 = biterr(double(decoded1(tblen+1:end),msg(1:end-tblen);num2,rat2 = biterr(double(decoded2(tblen+1:end),msg(1:end-tblen);ber0(n,x) = rat0;b