Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / communications-1.1.1 / convenc.m

diff --git a/octave_packages/communications-1.1.1/convenc.m b/octave_packages/communications-1.1.1/convenc.m
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+## Copyright (C) 2012 Tony Richardson <richardson.tony@gmailcom>
+##
+## This program is free software; you can redistribute it and/or modify it under
+## the terms of the GNU General Public License as published by the Free Software
+## Foundation; either version 3 of the License, or (at your option) any later
+## version.
+##
+## This program is distributed in the hope that it will be useful, but WITHOUT
+## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+## details.
+##
+## You should have received a copy of the GNU General Public License along with
+## this program; if not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{x} =} convenc (@var{m}, @var{G}, @var{k})
+## Compute output of an (n, @var{k}, L) convolutional encoder with vector input
+## @var{m} and matrix of generator polynomials @var{G}.
+##
+## The input vector @var{m} can be of arbitrary length. @var{G} is a matrix with n rows
+## and @var{k}*(L+1) columns. The rows of @var{G} are the generator polynomials for each
+## of the n output bits (per @var{k} input bits).
+##
+## The output is a vector whose length is n*floor([length(@var{m})+@var{k}*(L+1)-1]/@var{k}).
+## If unspecified, @var{k} defaults to 1.
+##
+## Example 1: Compute the output from a (2, 1, 2) convolutional encoder
+## @example
+## @group
+## m  = [ 1 1 0 1 1 1 0 0 1 0 0 0];
+## g1 = [1 1 1];
+## g2 = [1 0 1];
+## convenc (m, [g1; g2])
+##      @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]
+## @end group
+## @end example
+##
+## Example 2: Compute the output from a (3, 2, 1) convolutional encoder
+## @example
+## @group
+## m  = [0 1 1 0 0 0 1 1 ];
+## g1 = [1 0 1 1];
+## g2 = [1 1 0 1];
+## g3 = [1 0 1 0];
+## convenc (m, [g1; g2; g3], 2)
+##      @result{} [1 1 1 1 1 1 1 1 0 1 0 1]
+## @end group
+## @end example
+##
+## @strong{Caution:}: this function is not compatible with @sc{matlab}'s convenc().
+## @end deftypefn
+
+function x = convenc (m, G, k = 1)
+  if (nargin < 2 || nargin > 3)
+    print_usage;
+  endif
+
+                                # Use conv2 to do repeated 1d convolutions of m with each row of G. 
+                                # rem is used to transform the standard convolution result to one
+                                # which uses modulo-2 addition.  Only cols with index a mult. of k 
+                                # are in the actual enc. output
+
+  x = rem(conv2(1, m(:)', G),2)(:,!rem(1:numel(m),k))(:)';
+endfunction