CCS - Channel Capacity and Coding - Channel Coding - Convolutional Codes

 1 % MATLAB script for Illustrative Problem 10.13.
 2 k0=2;
 3 g=[0 0 1 0 1 0 0 1;0 0 0 0 0 0 0 1;1 0 0 0 0 0 0 1];
 4 input=[1 0 0 1 1 1 0 0 1 1 0 0 0 0 1 1 1];
 5 output=cnv_encd(g,k0,input);
 6 
 7 
 8 function output=cnv_encd(g,k0,input)
 9 %          cnv_encd(g,k0,input)
10 %          determines the output sequence of a binary convolutional encoder
11 %          g is the generator matrix of the convolutional code
12 %            with n0 rows and l*k0 columns. Its rows are g1,g2,...,gn.
13 %          k0 is the number of bits entering the encoder at each clock cycle.
14 %          input is the binary input seq.
15 
16 %  Check to see if extra zero-padding is necessary.
17 if rem(length(input),k0) > 0
18   input=[input,zeros(size(1:k0-rem(length(input),k0)))];
19 end
20 n=length(input)/k0;
21 %  Check the size of matrix g.
22 if rem(size(g,2),k0) > 0
23   error(‘Error, g is not of the right size.‘)
24 end
25 %  Determine l and n0.
26 l=size(g,2)/k0;
27 n0=size(g,1);
28 %  add extra zeros
29 u=[zeros(size(1:(l-1)*k0)),input,zeros(size(1:(l-1)*k0))];
30 %  Generate uu, a matrix whose columns are the contents of 
31 %  conv. encoder at various clock cycles.
32 u1=u(l*k0:-1:1);
33 for i=1:n+l-2
34   u1=[u1,u((i+l)*k0:-1:i*k0+1)];
35 end
36 uu=reshape(u1,l*k0,n+l-1);
37 %  Determine the output
38 output=reshape(rem(g*uu,2),1,n0*(l+n-1));

>> output

output =

Columns 1 through 20

0 0 0 0 0 1 1 0 1 1 1 1 1 0 1 0 1 1 1 0

Columns 21 through 36

0 1 1 0 1 0 0 1 0 0 1 1 1 1 1 1