octave-communications-common 1.2.0-1build1 / usr / share / octave / packages / communications-1.2.0 / modmap.m

## 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} {} modmap (@var{method}, @dots{})
## @deftypefnx {Function File} {y =} modmap (@var{x}, @var{fd}, @var{fs}, "ask", @var{m})
## @deftypefnx {Function File} {y =} modmap (@var{x}, @var{fd}, @var{fs}, "fsk", @var{m}, @var{tone})
## @deftypefnx {Function File} {y =} modmap (@var{x}, @var{fd}, @var{fs}, "msk")
## @deftypefnx {Function File} {y =} modmap (@var{x}, @var{fd}, @var{fs}, "psk", @var{m})
## @deftypefnx {Function File} {y =} modmap (@var{x}, @var{fd}, @var{fs}, "qask", @var{m})
## @deftypefnx {Function File} {y =} modmap (@var{x}, @var{fd}, @var{fs}, "qask/cir", @var{nsig}, @var{amp}, @var{phs})
## @deftypefnx {Function File} {y =} modmap (@var{x}, @var{fd}, @var{fs}, "qask/arb", @var{inphase}, @var{quadr})
## @deftypefnx {Function File} {y =} modmap (@var{x}, @var{fd}, @var{fs}, "qask/arb", @var{map})
##
## Mapping of a digital signal to an analog signal. With no output arguments
## @code{modmap} plots the constellation of the mapping. In this case the
## first argument must be the string @var{method} defining one of "ask",
## "fsk", "msk", "qask", "qask/cir" or "qask/arb". The arguments following
## the string @var{method} are generally the same as those after the
## corresponding string in the function call without output arguments.
## The exception is @code{modmap ("msk", @var{Fd})}.
##
## With an output argument, @var{y} is the complex mapped analog signal. In
## this case the arguments @var{x}, @var{fd} and @var{fs} are required. The
## variable @var{x} is the digital signal to be mapped, @var{fd} is the
## sampling rate of the of digital signal and the @var{fs} is the sampling
## rate of the analog signal. 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"
## Quadrature 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.
##
## The additional argument @var{m} is the order of the modulation to use.
## @var{m} must be larger than the largest element of @var{x}. The variable
## @var{tone} is the FSK tone to use in the modulation.
##
## For "qask/cir", the additional arguments are the same as for
## @code{apkconst}, and you are referred to @code{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 @code{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}.
## @seealso{demodmap, dmodce, amodce, apkconst, qaskenco}
## @end deftypefn

function y = modmap (varargin)

  method = "sample";
  if (nargout == 0)
    if (nargin < 1)
      error ("modmap: too few arguments");
    endif
    method = varargin{1};
    optarg = 1;
    M = 2;
    fd = 1;
    fs = 1;
  elseif (nargout == 1)
    if (nargin < 3)
      error ("modmap: too few arguments");
    endif
    x = varargin{1};
    fd = varargin{2};
    fs = varargin{3};
    if (nargin > 3)
      method = varargin{4};
    endif
    M = max (2, 2^ceil (log2 (max (x(:)) + 1)));
    optarg = 4;

    if (!isscalar (fs) || !isscalar (fd) || !isreal (fs) || !isreal (fd) || ...
        (fs <= 0) || (fd <= 0))
      error ("modmap: FD and FS must be positive real values");
    endif
    if (abs (fs/fd - fix (fs/fd)) > eps)
      error ("modmap: FS must be an integer multiple of FD");
    endif

    nn = round (fs/fd);
    if (min (size (x)) == 1)
      n = length (x);
      yy = zeros (n, 1);
      if (size (x, 1) == 1)
        yy = yy';
      endif
      for i = 1:nn
        yy(i:nn:nn*n) = x;
      endfor
    else
      n = size (x, 1);
      yy = zeros (n*nn, size (x, 2));
      for i = 1:nn
        yy(i:nn:nn*n,:) = x;
      endfor
    endif
    x = yy;
  else
    error ("modmap: too many output arguments");
  endif

  if (!ischar (method))
    error ("modmap: METHOD must be a string");
  endif

  if (isempty (findstr (method, "/arb")) && isempty (findstr (method, "/cir")))
    if (nargin > optarg)
      M = varargin{optarg+1};
      if (! (isscalar (M) && isreal (M) && M == fix (M) && M >= 0))
        error ("modmap: M must be a positive integer");
      endif
    endif
    if (nargout != 0 && M < max (x(:)) + 1)
      error ("modmap: M must be greater than all elements of X");
    endif
  endif

  if (strcmp (method, "ask"))
    if (nargin > optarg + 1)
      error ("modmap: too many arguments");
    endif

    if (nargout == 0)
      if (M/2 == floor (M/2))
        apkconst (2*ones (1, M/2), 2*([1:M/2]-0.5)/(M-1));
      else
        apkconst ([1, 2*ones(1, floor (M/2))], 2*([0:floor(M/2)])/(M-1));
      endif
    else
      if (M/2 == floor (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
      y = c(x+1);
      if (size (x, 2) == 1)
        y = y';
      endif
    endif
  elseif (strcmp (method, "psk"))
    if (nargin > optarg + 1)
      error ("modmap: too many arguments");
    endif
    if (nargout == 0)
      apkconst (M, "n");
    else
      c = apkconst (M);
      y = c(x+1);
      if (size (x, 2) == 1)
        y = y';
      endif
    endif
  elseif (strcmp (method, "msk"))

    if (nargout == 0)
      if (nargin > optarg)
        fd = varargin{optarg+1};
        if (!isscalar (fd))
          error ("modmap: FD must be a scalar");
        endif
      endif
      if (nargin > optarg + 1)
        error ("modmap: too many arguments");
      endif

      ## This is an ugly plot, with little info. But hey!!!
      try stem ([0, fd], [2, 1]);
      catch
        error ("modmap: cannot find stem-plot function");
      end_try_catch
      title ("MSK constellation");
      xlabel ("Frequency (Hz)");
      ylabel ("");
      axis ([-fd, 2*fd, 0, 2]);
    else
      if (nargin > optarg)
        error ("modmap: too many arguments");
      endif
      tone = fd/2;
      y = tone * x;
    endif
  elseif (strcmp (method, "fsk"))
    if (nargin > optarg + 1)
      tone = varargin{optarg+2};
      if (!isscalar (tone))
        error ("modmap: TONE must be a scalar");
      endif
    else
      tone = fd;
    endif
    if (nargin > optarg + 2)
      error ("modmap: too many arguments");
    endif

    if (nargout == 0)
      ## This is an ugly plot, with little info. But hey!!!
      try stem ([0:tone:(M-1)*tone], [2, ones(1, M-1)]);
      catch
        error ("modmap: can not find stem-plot function");
      end_try_catch
      title ("FSK constellation");
      xlabel ("Frequency (Hz)");
      ylabel ("");
      axis ([-tone, M*tone, 0, 2]);
    else
      y = tone * x;
    endif
  elseif ((strcmp (method, "qask")) || (strcmp (method, "qsk")) || ...
          (strcmp (method, "qam")))
    if (nargin > optarg + 1)
      error ("modmap: too many arguments");
    endif
    if (nargout == 0)
      qaskenco (M);
    else
      y = qaskenco (x, M);
    endif
  elseif ((strcmp (method, "qask/cir")) || (strcmp (method, "qsk/cir")) || ...
          (strcmp (method, "qam/cir")))
    nsig = M;
    amp = [];
    phs = [];
    if (nargin > optarg)
      nsig = varargin{optarg+1};
      if (!isvector (nsig) || sum (nsig) < M)
        error ("modmap: NSIG must be a vector of M constellation points for METHOD qask/cir");
      endif
    endif
    if (nargin > optarg + 1)
      amp = varargin{optarg+2};
    endif
    if (nargin > optarg + 2)
      phs = varargin{optarg+3};
    endif
    if (nargout == 0)
      apkconst (nsig, amp, phs, "n");
    else
      c = apkconst (nsig, amp, phs);
      y = c(x+1);
      if (size (x, 2) == 1)
        y = y';
      endif
    endif
  elseif ((strcmp (method, "qask/arb")) || (strcmp (method, "qsk/arb")) || ...
          (strcmp (method, "qam/arb")))
    if (nargin == optarg)
      [inphase, quadr] = qaskenco (M);
    elseif (nargin == optarg+1)
      c = varargin{optarg+1};
      inphase = real (c);
      quadr = imag (c);
    elseif (nargin == optarg+2)
      inphase = varargin{optarg+1};
      quadr = varargin{optarg+2};
    else
      error ("modmap: too many arguments");
    endif
    if (!isreal (inphase) || !isreal (quadr) || !isvector (inphase) || ...
        !isvector (quadr) || !all (isfinite (inphase)) || ...
        !all (isfinite (quadr)) || (length (inphase) < M))
      error ("modmap: invalid mapping for METHOD qask/arb");
    endif

    if (nargout == 0)
      inphase = inphase(:);
      quadr = quadr(:);
      plot (inphase, quadr, "+r");
      title ("QASK Constellation");
      xlabel ("In-phase");
      ylabel ("Quadrature");
      axis ([min(inphase) - 1, max(inphase) + 1, min(quadr) - 1, max(quadr) + 1]);
      xd = 0.02 * max (inphase);
      if (nargin == 2)
        msg = msg(:);
        for i = 1:length (inphase)
          text (inphase(i)+xd, quadr(i), num2str (msg(i)));
        endfor
      else
        for i = 1:length (inphase)
          text (inphase(i)+xd, quadr(i), num2str (i-1));
        endfor
      endif
      refresh;
    else
      y = inphase(x+1) + 1i * quadr(x+1);
      if (size (x, 2) == 1)
        y = y';
      endif
    endif
  elseif (strcmp (method, "sample"))
    if (nargout == 0)
      error ("modmap: no constellation for resampling");
    endif
    ## Just for resampling !!! So don't need anything else here
    y = x;
  else
    error ("modmap: invalid mapping METHOD '%s'", method);
  endif

endfunction

%% Test input validation
%!error modmap ()
%!error modmap (1, 0, 0)