qaskdeco.m

数字通信第四版原书的例程

function [msg]=qaskdeco(x,y,m,minmax)
%QASKDECO Decodes QASK mapped signal back to integer symbols.
%       MSG = QASKDECO(X, Y, M) decodes the message signal MSG from the
%       in-phase component X and quadrature component Y with the M-ary
%       number M. M must equals to 2^K with K being an positive integer. The
%       minimum and the maximum number are assumed to be the same as the
%       output from QASKENCO.
%
%       MSG = QASKDECO(X, Y, M, MINMAX) decodes the information where
%       the maximum and minimum values of X and Y are given in the MINMAX
%       by the form:
%                    | X_min    X_max |
%           MINMAX = |                |
%                    | Y_min    Y_max |
%
%       See also: QASKENCO.

%       Wes Wang 10/11/95.
%       Copyright (c) 1995-96 by The MathWorks, Inc.
%       $Revision: 1.1 $  $Date: 1996/04/01 18:01:44 $

error(nargchk(1,4,nargin));
if (nargin <= 2) | (nargin > 4)
    error('Wrong number of input arguments.')
end;

if (nargin == 4)
    [i,j]=size(minmax);
    if (i ~= 2) | (j ~= 2)
        error('The fourth varaible in calling QASKDECO is incorrect.')
    end;
    if ((minmax(1,2) <= minmax(1,1)) | (minmax(2,2) <= minmax(2,1))) & (m > 2)
        disp('Cannot process QASKDECO')
        disp('The fourth variable should have the format:')
        disp('     | X_min    X_max |')
        disp('     | Y_min    Y_max |')
    end;
    if m > 2
        x = (x - minmax(1,1))/(minmax(1,2) - minmax(1,1));
    end
    if m > 0
        y = (y - minmax(2,1))/(minmax(2,2) - minmax(2,1));
    end;
    if (m == 2)
        y = y * 2 - 1;        
    elseif (m == 4)
        x = x * 2 - 1;
        y = y * 2 - 1;
    elseif (m == 8) | (m == 16)
        x = x * 6 - 3;
        y = y * 6 - 3;
    elseif (m == 32)
        x = x * 10 - 5;
        y = y * 10 - 5;
    elseif (m == 64)
        x = x * 14 - 7;
        y = y * 14 - 7;
    elseif (m == 128)
        x = x * 22 - 11; 
        y = y * 22 - 11; 
    elseif (m == 256)
        x = x * 30 - 11; 
        y = y * 30 - 11; 
    else
        error('M-ary number for QASKDECO must be 2, 4, 8, 16, 32, 64, 128, or 256')
    end;
end;
inx = find(x<=0);
if ~isempty(inx)
    x(inx) = abs(x(inx)) + 1;
end;
iny = find(y<=0);
if ~isempty(iny)
    y(iny) = abs(y(iny)) + 1;
end;
tab = [  1,  2,  9, 10, 17, 18, 49, 50, 97, 98,113,114,145,146,177,178
         3,  4, 11, 12, 19, 20, 51, 52, 99,100,115,116,147,148,179,180
         5,  6, 13, 14, 21, 22, 53, 54,101,102,117,118,149,150,181,182
         7,  8, 15, 16, 23, 24, 55, 56,103,104,119,120,151,152,183,184
        25, 26, 29, 30, 33, 34, 37, 38,105,106,121,122,153,154,185,186
        27, 28, 31, 32, 35, 36, 39, 40,107,108,123,124,155,156,187,188
        57, 58, 61, 62, 41, 42, 45, 46,109,110,125,126,157,158,189,190
        59, 60, 63, 64, 43, 44, 47, 48,111,112,127,128,159,160,191,192
        65, 66, 69, 70, 73, 74, 77, 78,129,130,133,134,161,162,193,194
        67, 68, 71, 72, 75, 76, 79, 80,131,132,135,136,163,164,195,196
        81, 82, 85, 86, 89, 90, 93, 94,137,138,141,142,165,166,197,198
        83, 84, 87, 88, 91, 92, 95, 96,139,140,143,144,167,168,199,200
       209,210,217,218,225,226,233,234,241,242,249,250,169,170,201,202
       211,212,219,220,227,228,235,236,243,244,251,252,171,172,203,204
       213,214,221,222,229,230,237,238,245,246,253,254,173,174,205,206
       215,216,223,224,231,232,239,240,247,248,255,256,175,176,207,208];
if (m=='fetch')
    msg=tab(1:x,1:y);
else
    [x_m, x_n] = size(x);
    [y_m, y_n] = size(y);
    if min(x_m, x_n) * min(y_m, y_n) ~= 1
        error('Input X and Y must be vectors.');
    end;
    for i = 1 : min(length(x), length(y));
        msg(i) = tab(x(i), y(i));
    end;
    if x_m > x_n
        msg = msg';
    end;
end;
msg = msg - 1;

%---end qaskdeco.m--