code_uncode.m

基与matalab的编码程序 已经调试通过

clear
close all
clc
pe_1(1,41)=0;
pe_2(1,41)=0;
eb=1;%one bit energy
a=[1 1 0 0 1 0 0 1 0 1];%编码前的数据
%----------------
c=2*a-1;      %未编码的bpsk映射
%----------------
%NRZI编码
re(1)=a(1);
for i=2:10
    re(i)=xor(re(i-1),a(i));
end
%--------------------
b=2*re-1;%bpsk映射，将0，1转换成1和－1
%--------------------

for s_n=-20:1:20
c_n=awgn(c,s_n)
re_n=awgn(b,s_n);%加噪

d0=zeros(1,10);%for state0's route
d1=zeros(1,10);%for state1's route
rece=zeros(1,10);%decoded serial


d_0(1)=(re_n(1)+sqrt(eb))^2;%d_0:sum of accumulation for state 0
d_1(1)=(re_n(1)-sqrt(eb))^2;%d_1:sum of accumulation for state 0
d0(1)=-1;
d1(1)=1;
for i=2:10
d00=(re_n(i)+sqrt(eb))^2;%每个时刻到0 的度量值

d_0(i)=min(d_0(i-1)+d00,d_1(i-1)+d00);
if d_0(i)==d_0(i-1)+d00
    d0(1:i)=[d0(1:i-1),0];
else
    d0(1:i)=[d1(1:i-1),1];
end
d11=(re_n(i)-sqrt(eb))^2;%每个时刻到1 的度量值

d_1(i)=min(d_0(i-1)+d11,d_1(i-1)+d11);
if d_1(i)==d_0(i-1)+d11
    d1(1:i)=[d0(1:i-1),1];
else
    d1(1:i)=[d1(1:i-1),0];
end
%---
if i>=6
if d_0(i)<=d_1(i)
    rece(i-5)=d0(i-5);
else
    rece(i-5)=d1(i-5);
end
end
end
%-----------------------------
%decoding of the last five bits
%==========
if  d_0(10)<=d_1(10)
    rece(6:10)=d0(6:10);
else
    rece(6:10)=d1(6:10);
end
%-------------
flag=0;
for i=1:10
    if rece(i)~=a(i)
        flag=flag+1;
    end
end
pe1(s_n+21)=flag/10;
%--------------------

 for i=1:10             %judge the output:1 or -1         
if c_n(i)>0;
    c_esti(i)=1;
else 
    c_esti(i)=0;
end
end
%----------------------
 flag=0;                      %the number of error bit
 for i=1:10
     if c_esti(i)~=c(i)       %not equal to the source signal,it's an error bit
         flag=flag+1;
     end
 end
 pe2(s_n+21)=flag/10;         %aquire the error rate
 flag=0;      
end
%-----------------------
%=======================
s_n=-20:1:20;
%subplot(2,1,1);
%plot(s_n,pe1(s_n+21));

%subplot(2,1,2);
%plot(s_n,pe2(s_n+21));
plot(s_n,pe1(s_n+21),'r-',s_n,pe2(s_n+21),'b--'),grid on  %r-为红色实线，为编码后的，b--为蓝色虚线，为未编码的