--- /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} {z = } demodmap (@var{y},@var{fd},@var{fs},'ask',@var{m})
+## @deftypefnx {Function File} {z = } demodmap (@var{y},@var{fd},@var{fs},'fsk',@var{m},@var{tone})
+## @deftypefnx {Function File} {z = } demodmap (@var{y},@var{fd},@var{fs},'msk')
+## @deftypefnx {Function File} {z = } demodmap (@var{y},@var{fd},@var{fs},'psk',@var{m})
+## @deftypefnx {Function File} {z = } demodmap (@var{y},@var{fd},@var{fs},'qask',@var{m})
+## @deftypefnx {Function File} {z = } demodmap (@var{y},@var{fd},@var{fs},'qask/cir',@var{nsig},@var{amp},@var{phs})
+## @deftypefnx {Function File} {z = } demodmap (@var{y},@var{fd},@var{fs},'qask/arb',@var{inphase},@var{quadr})
+## @deftypefnx {Function File} {z = } demodmap (@var{y},@var{fd},@var{fs},'qask/arb',@var{map})
+## @deftypefnx {Function File} {z = } demodmap (@var{y},[@var{fd}, @var{off}],@var{...})
+##
+## Demapping of an analog signal to a digital signal. The function
+## @dfn{demodmap} must have at least three input arguments and one
+## output argument. Argument @var{y} is a complex variable representing
+## the analog signal to be demapped. The variables @var{fd} and @var{fs} are
+## the sampling rate of the of digital signal and the sampling rate of the
+## analog signal respectively. It is required that @code{@var{fs}/@var{fd}}
+## is an integer.
+##
+## The available mapping of the digital signal are
+##
+## @table @asis
+## @item 'ask'
+## Amplitude shift keying
+## @item 'fsk'
+## Frequency shift keying
+## @item 'msk'
+## Minimum shift keying
+## @item 'psk'
+## Phase shift keying
+## @item 'qask'
+## @itemx 'qsk'
+## @itemx 'qam'
+## Quadraure amplitude shift keying
+## @end table
+##
+## In addition the 'qask', 'qsk' and 'qam' method can be modified with the
+## flags '/cir' or '/arb'. That is 'qask/cir' and 'qask/arb', etc are valid
+## methods and give circular- and arbitrary-qask mappings respectively. Also
+## the method 'fsk' and 'msk' can be modified with the flag '/max', in
+## which case @var{y} is assumed to be a matrix with @var{m} columns,
+## representing the symbol correlations.
+##
+## The variable @var{m} is the order of the modulation to use. By default
+## this is 2, and in general should be specified.
+##
+## For 'qask/cir', the additional arguments are the same as for
+## @dfn{apkconst}, and you are referred to @dfn{apkconst} for the definitions
+## of the additional variables.
+##
+## For 'qask/arb', the additional arguments @var{inphase} and @var{quadr} give
+## the in-phase and quadrature components of the mapping, in a similar mapping
+## to the outputs of @dfn{qaskenco} with one argument. Similar @var{map}
+## represents the in-phase and quadrature components of the mapping as
+## the real and imaginary parts of the variable @var{map}.
+## @end deftypefn
+## @seealso{modmap,ddemodce,ademodce,apkconst,qaskenco}
+
+function z = demodmap (y, fd, fs, varargin)
+
+ if (nargin < 3)
+ error ("demodmap: too few arguments");
+ endif
+
+ if (!isscalar(fs) || !isreal(fs) || !isreal(fd) ||(fs <= 0) || (fd <= 0))
+ error ("demodmap: sampling rates must be positive real values");
+ endif
+ if (abs(fs/fd - floor(fs/fd)) > eps)
+ error ("demodmap: the sample rate Fs must be an integer multiple of Fd");
+ endif
+
+ if (!isscalar(fd))
+ if (isequal(size(fd),[1,2]))
+ off = fd(2);
+ fd = fd(1);
+ else
+ error ("demodmap: sampling rate Fd must be a scalar or two-element row-vector");
+ endif
+ else
+ off = 0;
+ endif
+
+ if (nargin > 3)
+ method = varargin{1};
+ if (!ischar(method) || (!strcmp(method,"ask") && ...
+ isempty(findstr(method,"msk")) && isempty(findstr(method,"fsk")) && ...
+ isempty(findstr(method,"samp")) && !strcmp(method,"psk") && ...
+ !strcmp(method,"qask") && !strcmp(method,"qam") && ...
+ !strcmp(method,"qsk") && !strcmp(method,"qask/cir") && ...
+ !strcmp(method,"qam/cir") && !strcmp(method,"qsk/cir") && ...
+ !strcmp(method,"qask/arb") && !strcmp(method,"qam/arb") && ...
+ !strcmp(method,"qsk/arb")))
+ error ("modmap: unknown mapping method");
+ endif
+ else
+ method = "sample";
+ endif
+
+ if (!isreal(off) || (off < 0) || (off != floor(off)) || ...
+ (off >= fs/fd))
+ error ("demodmap: offset must be an integer in the range [0, Fs/Fd)");
+ endif
+ if (off == 0)
+ off = round(fs/fd);
+ endif
+
+ if (min(size(y)) == 1)
+ y = y(off:round(fs/fd):length(y));
+ else
+ y = y(off:round(fs/fd):size(y,1),:);
+ endif
+
+ if (strcmp(method,"ask") || !isempty(findstr(method,"fsk")) || ...
+ strcmp(method,"psk") || strcmp(method,"qask") || ...
+ strcmp(method,"qam") || strcmp(method,"qsk"))
+ if (nargin > 4)
+ M = varargin{2};
+ else
+ M = 2;
+ endif
+ if (!isempty(findstr(method,"fsk")) && (nargin > 5))
+ error ("demodmap: too many arguments");
+ endif
+ endif
+
+ z = [];
+ if (!isempty(findstr(method,"fsk")) || !isempty(findstr(method,"msk")))
+ if (findstr(method,"msk"))
+ if (nargin > 4)
+ error ("demodmap: too many arguments");
+ endif
+ M = 2;
+ tone = fd/2;
+ else
+ if (nargin > 5)
+ tone = varargin{3};
+ else
+ tone = fd;
+ endif
+ if (nargin > 6)
+ error ("demodmap: too many arguments");
+ endif
+ endif
+
+ if (findstr(method,"/max"))
+ if (size(y,2) != M)
+ error ("demodmap: when using correlation must have M columns");
+ endif
+ ## We have an M-column maximum from which with pick index of the maximum
+ ## value in each row as the decoded value
+ [a, b] = max(y');
+ z = (b - 1)';
+ else
+ c = [0:M-1]*tone;
+ endif
+ elseif (strcmp(method,"ask"))
+ if (floor(M/2) == M/2)
+ c = [ -2*([M/2:-1:1]-0.5)/(M-1), 2*([1:M/2]-0.5)/(M-1)];
+ else
+ c = [ -2*([floor(M/2):-1:1])/(M-1), 0, 2*([1:floor(M/2)])/(M-1)];
+ endif
+ elseif (strcmp(method,"psk"))
+ c = apkconst(M,[],[]);
+ elseif (!isempty(findstr(method,"qask")) || ...
+ !isempty(findstr(method,"qsk")) || ...
+ !isempty(findstr(method,"qam")))
+ if (findstr(method,"/cir"))
+ nsig = 2;
+ amp = [];
+ phs = [];
+ if (nargin > 4)
+ nsig = varargin{2};
+ if (!isvector(nsig))
+ error ("modmap: invalid number of constellation point in qask/cir");
+ endif
+ endif
+ if (nargin > 5)
+ amp = varargin{3};
+ endif
+ if (nargin > 6)
+ phs = varargin{4};
+ endif
+ c = apkconst(nsig,amp,phs);
+ M = length(c);
+ elseif (findstr(method,"/arb"))
+ if (nargin == 4)
+ c = qaskenco(2);
+ elseif (nargin == 5)
+ c = varargin{2};
+ elseif (nargin == 6)
+ inphase = varargin{2};
+ quadr = varargin{3};
+ c = inphase + 1i*quadr;
+ elseif (nargin > 6)
+ error ("demodmap: too many arguments");
+ endif
+ M = length(c);
+ else
+ ## Could do "c = qaskenco(M)", but qaskdeco's speed is not dependent
+ ## on M, while speed of code below is O(M).
+ z = qaskdeco(y,M);
+ endif
+ endif
+
+ ## Have we decoded yet? If not have a mapping that we can use.
+ if (isempty(z))
+ c = c(:);
+ z = zeros(size(y));
+ if (size(y,1) == 1)
+ [a, b] = min(abs(repmat(y(:).',M,1) - repmat(c,1,size(y,2))));
+ z = b - 1;
+ elseif (size(y,1) == 1)
+ [a, b] = min(abs(repmat(y(:),M,1) - repmat(c,1,size(y,1))));
+ z = (b - 1).';
+ else
+ for i=1:size(y,1)
+ [a, b] = min(abs(repmat(y(i,:),M,1) - repmat(c,1,size(y,2))));
+ z(i,:) = b - 1;
+ end
+ endif
+ endif
+
+endfunction
+
+
git://git.creatis.insa-lyon.fr / CreaPhase.git / blobdiff