卷积码编译码实验报告

厦门理工学院实验报告书

课程名称：信息论与编码实验

实验名称：卷积码编译码

m 个有效的寄存器单元，而输出移位寄存器仅中输入移位寄存器最多只有k

起一个并串转换作用。因此称参量m为卷积吗的记忆长度（段）

2、维比特译码原理

它的基本思想是把接收到的矢量，和网格图上诸种可能的路径比较，删去距离大的路径，保留距离小的路径，以距离最小路径作为发码的估值

五、实验内容

在MATLAB环境下卷积码编/解码器的实现。

1、主函数main.m

clear;clc;

msg = randint(1,20,[0,1])

word = encode_conv213(msg)

word(1) =~word(1); %信道中存在污染，人为的模拟传输过word(10) =~word(10); %程中的出错码字

word(15) =~word(15);

word1=word

msg_1 = decode_conv213(word1)

msg-msg_1

2 、状态积state_machine.m

function [output,nextState] = state_machine(input,current_state)

output(1) = mod(current_state(1)+current_state(3),2);

output(2) = mod(input+current_state(2)+current_state(1),2);

nextState(1) = current_state(2);

nextState(2) = current_state(3);

nextState(3) = input;

3、汉明距离hamming_distance.m

function distance = hamming_distance(a,b)

temp = a+b;

temp = mod(temp,2);

distance = sum(temp);

4 、213编码程序encode_conv213.m

function word = encode_conv213(msg)

word = zeros(1,length(msg)*2);

current = [0 0 0];

for i = 1:length(msg)

[out,next] = state_machine(msg(i),current);

current = next;

word(2*i-1) = out(1);

word(2*i) = out(2);

End

5、213维比特译码decode_conv213.m

function msg = decode_conv213(word)

chip = 10; %初始状态选十个信息

for i = 1:2^chip

M(i,:) = de2bi(i-1,chip); %把所有可能性按二进制输出

W(i,:) = encode_conv213(M(i,:));

%得到相应的二进制编译后的码字

D(i) = hamming_distance(W(i,:),word(1:chip*2));

%与出错码字对比得到汉明距

end

[val,index] = sort(D);

%val中存汉明距从小到大排列，index中存对应val数据所在位置

ret_msg = zeros(1,length(word)/2); %开辟译出码字的存放空间

for i = 1:6

%1024种选择6种最小距离，并输出在ret_msg中，最小汉明距存于ret_dis ret_msg(i,1:chip) = M(index(i),:);

ret_dis(i) = D(index(i));

end

iter = (length(word)-chip*2)/2; %剩余要译出的码字个数

for i=1:iter %迭代过程

for j=1:6

msg_temp1 = [ret_msg(j,1:chip+i-1) 0]; %下一状态出“0”

msg_temp2 = [ret_msg(j,1:chip+i-1) 1]; %下一状态出“1”

word_temp1 = encode_conv213(msg_temp1);

%下一状态为“0”时的编码

word_temp2 = encode_conv213(msg_temp2);

%下一状态为“1”时的编码

dis_temp1 = hamming_distance(word_temp1,word(1:chip*2+2*i));

dis_temp2 = hamming_distance(word_temp2,word(1:chip*2+2*i)); %算两种汉明距

if (dis_temp1

ret_msg(j,1:chip+i) = msg_temp1;

ret_dis(j) = dis_temp1;

else

ret_msg(j,1:chip+i) = msg_temp2;

ret_dis(j) = dis_temp2;

%选择较小汉明距的状态储存并输出在ret_msg中，最小汉明距存于ret_dis

end

end