Logo Search packages:      
Sourcecode: octave-communications version File versions  Download package

pskmod.m

## 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 2, 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; see the file COPYING.  If not, see
## <http://www.gnu.org/licenses/>.
##

## -*- texinfo -*-
## @deftypefn {Function File} {@var{y} = } pskmod (@var{x}, @var{m})
## @deftypefnx {Function File} {@var{y} = } pskmod (@var{x}, @var{m}, @var{phi})
## @deftypefnx {Function File} {@var{y} = } pskmod (@var{x}, @var{m}, @var{phi}, @var{type})
##
## Modulates an information sequence of integers @var{x} in the range 
## @code{[0 @dots{} M-1]} onto a complex baseband phase shift keying 
## modulated signal @var{y}. @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 QPSK is
##
## @example
## @group
## d = randint(1,5e3,4);
## y = pskmod(d,4,0,'Gray');
## z = awgn(y,30);
## plot(z,'rx')
##
## @end group
## @end example
## @end deftypefn
## @seealso{pskdemod}

function y=pskmod(x,M,phi,type)

m=0:M-1;

if ~isempty(find(ismember(x,m)==0))
      error("x elements should be integers in the set [0, M-1].");
endif 

if nargin<3
    phi=0;
endif

if nargin<4
      type="Bin";
endif 

constellation=exp(1j*2*pi*m/M+1j*phi);

if (strcmp(type,"Bin")||strcmp(type,"bin"))
    y=constellation(x+1);
elseif (strcmp(type,"Gray")||strcmp(type,"gray"))
    [a,b]=sort(bitxor(m,bitshift(m,-1)));
    y=constellation(b(x+1));
else
    usage("y = pskmod (x, M, [phi, [type]])");   
endif


%!assert (round(pskmod([0:3],4,0,'Bin')),[1 j -1 -j])
%!assert (round(pskmod([0:3],4,0,'Gray')),[1 j -j -1])

Generated by  Doxygen 1.6.0   Back to index