1 ## Copyright (C) 2012 Tony Richardson <richardson.tony@gmailcom>
3 ## This program is free software; you can redistribute it and/or modify it under
4 ## the terms of the GNU General Public License as published by the Free Software
5 ## Foundation; either version 3 of the License, or (at your option) any later
8 ## This program is distributed in the hope that it will be useful, but WITHOUT
9 ## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 ## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
13 ## You should have received a copy of the GNU General Public License along with
14 ## this program; if not, see <http://www.gnu.org/licenses/>.
17 ## @deftypefn {Function File} {@var{x} =} convenc (@var{m}, @var{G}, @var{k})
18 ## Compute output of an (n, @var{k}, L) convolutional encoder with vector input
19 ## @var{m} and matrix of generator polynomials @var{G}.
21 ## The input vector @var{m} can be of arbitrary length. @var{G} is a matrix with n rows
22 ## and @var{k}*(L+1) columns. The rows of @var{G} are the generator polynomials for each
23 ## of the n output bits (per @var{k} input bits).
25 ## The output is a vector whose length is n*floor([length(@var{m})+@var{k}*(L+1)-1]/@var{k}).
26 ## If unspecified, @var{k} defaults to 1.
28 ## Example 1: Compute the output from a (2, 1, 2) convolutional encoder
31 ## m = [ 1 1 0 1 1 1 0 0 1 0 0 0];
34 ## convenc (m, [g1; g2])
35 ## @result{} [1 1 0 1 0 1 0 0 0 1 1 0 0 1 1 1 1 1 1 0 1 1 0 0 0 0 0 0]
39 ## Example 2: Compute the output from a (3, 2, 1) convolutional encoder
42 ## m = [0 1 1 0 0 0 1 1 ];
46 ## convenc (m, [g1; g2; g3], 2)
47 ## @result{} [1 1 1 1 1 1 1 1 0 1 0 1]
51 ## @strong{Caution:}: this function is not compatible with @sc{matlab}'s convenc().
54 function x = convenc (m, G, k = 1)
55 if (nargin < 2 || nargin > 3)
59 # Use conv2 to do repeated 1d convolutions of m with each row of G.
60 # rem is used to transform the standard convolution result to one
61 # which uses modulo-2 addition. Only cols with index a mult. of k
62 # are in the actual enc. output
64 x = rem(conv2(1, m(:)', G),2)(:,!rem(1:numel(m),k))(:)';