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diff --git a/octave_packages/communications-1.1.1/pskdemod.m b/octave_packages/communications-1.1.1/pskdemod.m
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+## Copyright (C) 2006 Charalampos C. Tsimenidis
+##
+## 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{y} = } pamdemod (@var{x}, @var{m})
+## @deftypefnx {Function File} {@var{y} = } pamdemod (@var{x}, @var{m}, @var{phi})
+## @deftypefnx {Function File} {@var{y} = } pamdemod (@var{x}, @var{m}, @var{phi}, @var{type})
+##
+## Demodulates a complex-baseband phase shift keying modulated signal 
+## into an information sequence of integers in the range 
+## @code{[0 @dots{} M-1]}. @var{phi} controls the initial phase and 
+## @var{type} controls the constellation mapping. If @var{type} is set
+## to 'Bin' will result in binary encoding, in contrast, if set to 
+##'Gray' will give Gray encoding.  An example of Gray-encoded 8-PSK is
+##
+## @example
+## @group
+## d = randint(1,1e3,8);
+## y = pskmod(d,8,0,'Gray');
+## z = awgn(y,20);
+## d_est = pskdemod(z,8,0,'Gray');
+## plot(z,'rx')
+## biterr(d,d_est)
+## @end group
+## @end example
+## @end deftypefn
+## @seealso{pskmod}
+
+function y=pskdemod(x,M,phi,type)
+
+if nargin<2
+	usage("y = pskdemod (x, M, [phi, [type]])");   
+endif    
+
+if nargin<3
+	phi=0;
+endif
+
+if nargin<4
+	type="Bin";
+endif
+
+m=0:M-1;
+index=mod(round((arg(x)-phi)*M/2/pi),M)+1;
+
+if (strcmp(type,"Bin")||strcmp(type,"bin"))
+        y=index-1;
+elseif (strcmp(type,"Gray")||strcmp(type,"gray"))
+	map=bitxor(m,bitshift(m,-1));
+	y=map(index);
+else
+    usage("y = pskdemod (x, M, [phi, [type]])");   
+endif
+
+%!assert (pskdemod([1 j -1 -j],4,0,'Bin'),[0:3])
+%!assert (pskdemod([1 j -j -1],4,0,'Gray'),[0:3])