Add a useful package (from Source forge) for octave

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

diff --git a/octave_packages/communications-1.1.1/qamdemod.m b/octave_packages/communications-1.1.1/qamdemod.m
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+## Copyright (C) 2007 Sylvain Pelissier <sylvain.pelissier@gmail.com>
+## Copyright (C) 2009 Christian Neumair <cneumair@gnome.org>
+##
+## 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} qamdemod (@var{x},@var{m})
+## Create the QAM demodulation of x with a size of alphabet m.
+## @seealso{qammod,pskmod,pskdemod}
+## @end deftypefn
+
+function z = qamdemod(y,m)
+    if(nargin < 2)
+       usage('y = qamdemod(x,m)');
+       exit;
+   end
+    
+    c = sqrt(m);
+    if(c ~= fix(c)  || log2(c) ~= fix(log2(c)))
+        error('m must be a square of a power of 2');
+    end
+    
+    x = qammod(0:(m-1),m);
+    x = reshape(x,1,m);
+    z = zeros(size(y));
+    for k = 1:numel(y)
+        [n z(k)] = min(abs(y(k) - x));
+    end
+    z = z - 1;