mvitdecoder_2x.m

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function [Out,BlkSize] = mVitDecoder(In,BlkSize,mode,pmode,DemapScale)
% Viterbi Decoder for the FEC Decoder of IEEE 802.16-2004
% (WiMAX, OFDMA only)
%
%     [Out,BlkSize] = mVitDecoder(In,BlkSize,mode,pmode,DemapScale)
%
% In     : soft symbol input vector or matrix (values -128 to 127)
%          one column per code block.
% BlkSize: row vector, length = number of code blocks
%          number of data bits for each code block
% mode   : specifies the decoding mode
%          0 = CC    (tail-biting)
%          3 = ZT-CC (zero-tailing)
% pmode  : specifies the puncturing mode (0,1,2)
%          This parameter is only required for the tail-biting Viterbi which
%          is implemented using a temporary workaround.
% DemapScale: specifies the DemapScale mode ('y','n')
%          'y': use of 'soft'8
%          'n': use of 'unquant'
%
% Out    : binary output vector or matrix (values 0 or 1)
%          one column per code block.
%
% Note: Internally the input is rounded before decoding.
%
% Matlab Release 14SP2
% The communication toolbox is required.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%  Property of Freescale
%  Freescale Confidential Proprietary
%  Freescale Copyright (C) 2005 All rights reserved
%  ----------------------------------------------------------------------------
%  $RCSfile: mVitDecoder_2x.m.rca $
%  $Revision: 1.3 $
%  $Date: Tue Dec 19 17:00:30 2006 $
%  Target: Matlab
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

[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

if (DemapScale == 'y')
%     %round
%     Ins=In;
%     In=int8(In);
%     %   check input range
%     if (max(max(In))>127)|(min(min(In))<-128)
%         error('Error: Viterbi decoder input is out of range.');
%     end
%     %convert data to unsigned numbers
%     In = rescale(-Ins,'uint8','max',0.7); %option4=0.7 seems not too bad
In = -In + 127 ;
end

%define constant
t = poly2trellis(7,[171 133]);

switch mode,
    case 0  %tail-biting
        Out = logical(zeros(m/2,n));
        for b=1:n,
            temp = double([In(1:BlkSize(b),b);In(1:BlkSize(b),b)]);
            if (DemapScale == 'y')
                temp = vitdec(temp,t,BlkSize(b),'trunc','soft',8);
            else
                temp = vitdec(temp,t,BlkSize(b),'trunc','unquant');
            end
            Out(1:BlkSize(b)/2,b) = [temp(BlkSize(b)/2+1:BlkSize(b)/4+BlkSize(b)/2) ; temp(BlkSize(b)/4+1:BlkSize(b)/2)];
        end %for
        BlkSize=BlkSize/2;
    case 3  %zero-tailing
        Out = logical(zeros(m/2,n));
        for b=1:n,
            Out(1:BlkSize(b)/2,b) = vitdec(double(In(1:BlkSize(b),b)),t,3,'term','soft',8);
        end
        BlkSize=BlkSize/2-8;
    otherwise
        error('Error: Viterbi decoder mode unknown.');
end