Add a useful package (from Source forge) for octave

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

diff --git a/octave_packages/communications-1.1.1/pamdemod.m b/octave_packages/communications-1.1.1/pamdemod.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 pulse amplitude modulated signal @var{x} 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-PAM is
+##
+## @example
+## @group
+## d = randint(1,1e4,8);
+## y = pammod(d,8,0,'Gray');
+## z = awgn(y,20);
+## d_est = pamdemod(z,8,0,'Gray');
+## plot(z,'rx')
+## biterr(d,d_est)
+## @end group
+## @end example
+## @end deftypefn
+## @seealso{pammod}
+
+function y=pamdemod(x,M,phi,type)
+
+if nargin<2
+       usage("y = pamdemod (x, M, [phi, [type]])");   
+endif    
+
+if nargin<3
+       phi=0;
+endif
+
+if nargin<4
+       type="Bin";
+endif
+
+index=genqamdemod(x,[-M+1:2:M-1].*exp(-1j*phi));
+
+if (strcmp(type,"Bin")||strcmp(type,"bin"))
+        y=index;
+elseif (strcmp(type,"Gray")||strcmp(type,"gray"))
+       m=0:M-1;
+       map=bitxor(m,bitshift(m,-1));
+       y=map(index+1);
+else
+    usage("y = pamdemod (x, M, [phi, [type]])");   
+endif
+
+%!assert (pamdemod([-7:2:7],8,0,'Bin'),[0:7])
+%!assert (pamdemod([-7:2:7],8,0,'Gray'),[0 1 3 2 6 7 5 4])