--- /dev/null
+## Copyright (C) 2003 David Bateman
+##
+## 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{msg} =} qaskdeco (@var{c},@var{m})
+## @deftypefnx {Function File} {@var{msg} =} qaskdeco (@var{inphase},@var{quadr},@var{m})
+## @deftypefnx {Function File} {@var{msg} =} qaskdeco (@var{...},@var{mnmx})
+##
+## Demaps an analog signal using a square QASK constellation. The input signal
+## maybe either a complex variable @var{c}, or as two real variables
+## @var{inphase} and @var{quadr} representing the in-phase and quadrature
+## components of the signal.
+##
+## The argument @var{m} must be a positive integer power of 2. By deafult the
+## same constellation as created in @dfn{qaskenco} is used by @dfn{qaskdeco}.
+## If is possible to change the values of the minimum and maximum of the
+## in-phase and quadrature components of the constellation to account for
+## linear changes in the signal values in the received signal. The variable
+## @var{mnmx} is a 2-by-2 matrix of the following form
+##
+## @multitable @columnfractions 0.125 0.05 0.25 0.05 0.25 0.05
+## @item @tab | @tab min in-phase @tab , @tab max in-phase @tab |
+## @item @tab | @tab min quadrature @tab , @tab max quadrature @tab |
+## @end multitable
+##
+## If @code{sqrt(@var{m})} is an integer, then @dfn{qaskenco} uses a Gray
+## mapping. Otherwise, an attempt is made to create a nearly square mapping
+## with a minimum Hamming distance between adjacent constellation points.
+## @end deftypefn
+## @seealso{qaskenco}
+
+function a = qaskdeco(varargin)
+
+ have_mnmx = 0;
+ if (nargin == 2)
+ c = varargin{1};
+ inphase = real(c);
+ quadr = imag(c);
+ M = varargin{2};
+ elseif (nargin == 3)
+ if (all(size(varargin{3}) == [2 2]))
+ c = varargin{1};
+ inphase = real(c);
+ quadr = imag(c);
+ M = varargin{2};
+ mnmx = varargin{3};
+ have_mnmx = 1;
+ else
+ inphase = varargin{1};
+ quadr = varargin{2};
+ M = varargin{3};
+ endif
+ elseif (nargin == 4)
+ inphase = varargin{1};
+ quadr = varargin{2};
+ M = varargin{3};
+ mnmx = varargin{4};
+ have_mnmx = 1;
+ else
+ error ("qaskdeco: incorrect number of arguments");
+ endif
+
+ if (iscomplex(inphase) || iscomplex(quadr))
+ error ("qaskdeco: error in in-phase and/or quadrature components");
+ endif
+
+ if (!isscalar(M) || (M != ceil(M)) || (M < 2))
+ error ("qaskdeco: order of modulation must be a positive integer greater than 2");
+ endif
+
+ if (log2(M) != ceil(log2(M)))
+ error ("qaskdeco: the order must be a power of two");
+ endif
+
+ if (have_mnmx)
+ if (any(size(mnmx) != [2 2]))
+ error ("qaskdeco: error in max/min constellation values");
+ endif
+ else
+ if ((M == 2) || (M == 4))
+ mnmx = [-1, 1; -1, 1];
+ elseif (M == 8)
+ mnmx = [-3, 3; -1, 1];
+ elseif (sqrt(M) == floor(sqrt(M)))
+ NC = 2^floor(log2(sqrt(M)));
+ mnmx = [-NC+1, NC-1; -NC+1, NC-1];
+ else
+ NC = 2^floor(log2(sqrt(M))) + 2*sqrt(M/32);
+ mnmx = [-NC+1, NC-1; -NC+1, NC-1];
+ endif
+ endif
+
+ if (M == 2)
+ layout = [0, 1]';
+ elseif (M == 4)
+ layout = [0, 1; 2, 3];
+ elseif (M == 8)
+ layout = [4, 5; 0, 1; 2, 3; 6, 7];
+ else
+ NC =2^floor(log2(sqrt(M)));
+ MM = NC * NC;
+ Gray = [0 1];
+ for i=2:ceil(log2(NC))
+ Gray = [Gray 2^(i-1) + fliplr(Gray)];
+ end
+ Gray = fliplr(de2bi(shift(Gray,length(Gray)/2 - 1)));
+ Gray2 = zeros(MM,log2(MM));
+ Gray2(:,1:2:log2(MM)) = repmat(Gray,NC,1);
+ for i=1:NC
+ Gray2(i:NC:MM,2:2:log2(MM)) = Gray;
+ end
+ layout = reshape(bi2de(fliplr(Gray2)),NC,NC);
+
+ if (MM != M)
+ ## Not sure this is the best that can be done for these mappings. If
+ ## anyone wants to improve this, go ahead, but do it in qaskenco too.
+ OFF = sqrt(M/32);
+ NR = NC + 2*OFF;
+ layout2 = NaN * ones(NR);
+ layout2(1+OFF:OFF+NC,1+OFF:OFF+NC) = layout;
+
+ layout2(1:OFF,1+OFF:OFF+NC) = MM + layout(OFF:-1:1,:);
+ layout2(NR-OFF+1:NR,1+OFF:OFF+NC) = MM + layout(NC:-1:NC-OFF+1,:);
+
+ layout2(1+2*OFF:NC,1:OFF) = MM + layout(OFF+1:NC-OFF,OFF:-1:1);
+ layout2(1+2*OFF:NC,NR-OFF+1:NR) = MM + ...
+ layout(OFF+1:NC-OFF,NC:-1:NC-OFF+1);
+
+ layout2(1+OFF:2*OFF,1:OFF) = MM + ...
+ layout(NC/2:-1:NC/2-OFF+1,NC/2:-1:OFF+1);
+ layout2(NC+1:OFF+NC,1:OFF) = MM + ...
+ layout(NC-OFF:-1:NC/2+1,NC/2:-1:OFF+1);
+
+ layout2(1+OFF:2*OFF,NR-OFF+1:NR) = MM + ...
+ layout(NC/2:-1:NC/2-OFF+1,NC-OFF:-1:NC/2+1);
+ layout2(NC+1:OFF+NC,NR-OFF+1:NR) = MM + ...
+ layout(NC-OFF:-1:NC/2+1,NC-OFF:-1:NC/2+1);
+ layout = layout2;
+ endif
+ endif
+
+ ix = 1 + (inphase - mnmx(1,1))/(mnmx(1,2)-mnmx(1,1))*(size(layout,1)-1);
+ qx = 1 + (quadr - mnmx(2,1))/(mnmx(2,2)-mnmx(2,1))*(size(layout,2)-1);
+
+ try wfi = warning("off", "Octave:fortran-indexing");
+ catch wfi = 0;
+ end
+
+ unwind_protect
+ a = layout(size(layout,1)*(max(min(round(qx),size(layout,2)),1)-1) + ...
+ max(min(round(ix),size(layout,1)),1));
+ ## XXX FIXME XXX Why is this necessary??
+ if ((M == 2) &&(size(inphase,1) == 1))
+ a = a';
+ endif
+
+ if (any(isnan(a(:))))
+ ## We have a non-square constellation, with some invalid points.
+ ## Map to nearest valid constellation points...
+ indx = find(isnan(a(:)));
+ ix = ix(indx);
+ qx = qx(indx);
+ ang = atan2(quadr(indx),inphase(indx));
+
+ qx(find(ang > 3*pi/4)) = NR-OFF;
+ ix(find((ang <= 3*pi/4) & (ang > pi/2))) = OFF+1;
+ ix(find((ang <= pi/2) & (ang > pi/4))) = NR - OFF;
+ qx(find((ang <= pi/4) & (ang > 0))) = NR - OFF;
+ qx(find((ang <= 0) & (ang > -pi/4))) = OFF+1;
+ ix(find((ang <= -pi/4) & (ang > -pi/2))) = NR - OFF;
+ ix(find((ang <= -pi/2) & (ang > -3*pi/4))) = OFF+1;
+ qx(find(ang <= -3*pi/4)) = OFF+1;
+
+ a(indx) = layout(size(layout,1)*(max(min(round(qx), ...
+ size(layout,2)),1)-1) + max(min(round(ix),size(layout,1)),1));
+ endif
+ unwind_protect_cleanup
+ warning (wfi);
+ end_unwind_protect
+
+endfunction
+
+%!function dec = __fntestqask1__ (msg, m)
+%! [inp, qudr] = qaskenco (msg, m);
+%! dec = qaskdeco (inp, qudr, m);
+
+%!function __fntestqask2__ (m, dims)
+%! msg = floor( rand(dims) * m);
+%! assert (__fntestqask1__ (msg, m), msg);
+
+%!test __fntestqask2__ (2, [100,100])
+%!test __fntestqask2__ (4, [100,100])
+%!test __fntestqask2__ (8, [100,100])
+%!test __fntestqask2__ (16, [100,100])
+%!test __fntestqask2__ (32, [100,100])
+%!test __fntestqask2__ (64, [100,100])
+
+%!test __fntestqask2__ (2, [100,100,3])
+%!test __fntestqask2__ (4, [100,100,3])
+%!test __fntestqask2__ (8, [100,100,3])
+%!test __fntestqask2__ (16, [100,100,3])
+%!test __fntestqask2__ (32, [100,100,3])
+%!test __fntestqask2__ (64, [100,100,3])
git://git.creatis.insa-lyon.fr / CreaPhase.git / blobdiff