mdemodmapper.m

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%  Property of Freescale
%  Freescale Confidential Proprietary
%  Freescale Copyright (C) 2005 All rights reserved
%  ----------------------------------------------------------------------------
%  $RCSfile: mDemodMapper.m.rca $
%  $Revision: 1.9 $
%  $Date: Fri Jan 12 18:20:37 2007 $
%  Target: Matlab
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% Demodulation Mapping of IEEE 802.16-2004 (OFDMA, WiMAX)
%
%     [Out, BlkSize] = mDemodMapper(In,BlkSize,mode,d)
%
% In :    complex input column vector
%         Matrices are processed column by column, one vector per column.
%
% mode  : number of coded bits per complex soft symbol
%         2 = QPSK
%         4 = 16QAM
%         6 = 64QAM
%         The mode is the same for all code blocks.
%
%
% Out: soft symbol output vector ('int8', values -128 to 127)
%
% BlkSize: row vector, length = number of code blocks
%          number of data elements in each code block (or column)
%
% Matlab 7 Release 14 SP2

%-- Matlab files used by this file
%-- End of list

function [Out,BlkSize] = mDemodMapper(In,BlkSize,mode,DemapScale)

% Changed from a define..... %

[m,n]=size(In);

% check dimensions
[x,y]=size(BlkSize);
if ((x~=1)|(y~=n))
    error('Error: BlkSize must be row vector with the same number of columns as In.');
end

% Distance is calculated induvidually for each slot
InSlotUnits=reshape(In,48,[]);
switch mode
    case 2 %QPSK
        d=ones(48,1)*(mean(abs(double(InSlotUnits)))*cos(pi/4));
        d=reshape(d,m,n);
    case 4 %16QAM
        d=ones(48,1)*(mean(abs(double(InSlotUnits)))*cos(pi/4));
        d=reshape(d,m,n);
    case 6 %64QAM
        d=ones(48,1)*(mean(abs(double(InSlotUnits)))*cos(pi/4))/2;
        d=reshape(d,m,n);
    otherwise
        error('Error: Modulation mode %d not supported.',mode);
end

[x,y]=size(d);
if (x*y)==1
    d=d*ones(1,n);
end

if any(d<0)
    error('Error: Distance must be positive.')
end

switch mode
    case 2 %QPSK
        maxval = d;
        In = reshape(In,1,m,n);
        Out = reshape([real(In);imag(In)],m*2,n);
    case 4 %16QAM
        maxval = 2*d;
        d = reshape(d,1,m,n);
        In = double(reshape(In,1,m,n));
        b3 = real(In);
        b1 = imag(In);
        Out = reshape([b3;d-abs(b3);b1;d-abs(b1)],m*4,n);
    case 6 %64QAM
        maxval = 4*d;
        d = reshape(d,1,m,n);
        In = double(reshape(In,1,m,n));
        b5 = real(In);
        b4 = 2*d-abs(b5);
        b2 = imag(In);
        b1 = 2*d-abs(b2);
        Out = reshape([b5;b4;d-abs(b4);b2;b1;d-abs(b1)],m*6,n);
    otherwise
        error('Error: Modulation mode %d not supported.',mode);
end

BlkSize = BlkSize*mode;

if (DemapScale == 'y')
    % Normalize to max precision
    shift  = 7 - floor(log2(maxval+1e-300)); % 1e-300 is to eliminate log of 0
    shift  = (shift<=0) .* shift;  % saturate, avoid values greater than 0
    temp=shift.';
    for k=1:mode-1
        temp=[temp;shift.'];
    end
    shift=reshape(temp,n,m*mode).';
    Out = double(Out) .* (2.^shift);
    Out = int8(Out);
end