www.pudn.com > turboprog.rar > rsc_encode.m

function y = rsc_encode(g, x, terminated) 
% Copyright Nov. 1998 Yufei Wu 
% MPRG lab, Virginia Tech. 
% for academic use only 
 
% encodes a block of data x (0/1)with a recursive systematic 
% convolutional code with generator vectors in g, and 
% returns the output in y (0/1). 
% if terminated>0, the trellis is perfectly terminated 
% if terminated<0, it is left unterminated; 
 
% determine the constraint length (K), memory (m), and rate (1/n) 
% and number of information bits. 
[n,K] = size(g); 
m = K - 1; 
if terminated>0 
  L_info = length(x);   % L_info: lenght of information sequence?  -yzh 
  L_total = L_info + m; % L_total:m additional bits is used to terminate?  -yzh 
else 
  L_total = length(x); 
  L_info = L_total - m; % see the sequence for untermated in function encoderm for reason. length of x is L_total  --yzh 
end   
 
 
% initialize the state vector 
state = zeros(1,m); 
 
% generate the codeword 
for i = 1:L_total 
   if terminated<0 | (terminated>0 & i<=L_info) 
      d_k = x(1,i);     % d_k: information sequence -yzh 
   elseif terminated>0 & i>L_info 
      % terminate the trellis 
      d_k = rem( g(1,2:K)*state', 2 ); % g(1,2:K): why is g(1,2:K)? not other recursive polynomial?  -yzh 
   end 
   % a_k??feedback polynomial is g(1:)? --yzh 
   % for terminated>0 & i>L_info, a_k will be zero(heihei)  -yzh  
   % recursive encoding?right!    --yzh 
   a_k = rem( g(1,:)*[d_k state]', 2 );     % a_k: the bit to be put into the register    -yzh 
   [output_bits, state] = encode_bit(g, a_k, state); 
   % since systematic, first output is input bit 
   output_bits(1,1) = d_k; 
   y(n*(i-1)+1:n*i) = output_bits;  % n output bits for 1 input bit(recursiv encoder)  --yzh 
end