why unquantized comm.ViterbiDecoder gives bits with errors when the modulation is 1-2*encodedBits with 100dB say; the code is as follow:

% clear All clc

% initial data for encoding & decoding % codeRate = 1/2;

% constlen = 7;

% codegenpoly = [171 133];

% tblen = 32;

% trellis = poly2trellis ( constlen, codegenpoly );

% the three comm members: % ( 1 ) comm.ConvolutionalEncoder % ( 2 ) comm.AWGNChannel % ( 3 ) comm.ViterbiDecoder % hConEnc = comm.ConvolutionalEncoder ( trellis );

% hAWGN = comm.AWGNChannel ( 'NoiseMethod', 'Variance', 'Variance', 1 );

% EbNo = 40.0;

% noiseVar = 1. / ( 2 * codeRate * 10. ^ ( EbNo / 10 ) );

% hAWGN.Variance = noiseVar;

% hDec = comm.ViterbiDecoder ( trellis, ... 'InputFormat', 'Unquantized', 'TracebackDepth', tblen );

% the simulation loop % for counter = 1 : 5 % data = randi ( [0 1], 30, 1 );

    %
    encodedData = step ( hConEnc, data );

    % compatible unquantized received signal
    % 
     receivedSignal = step ( hAWGN,  (1 - 2 * encodedData)  );

    %
    receivedBits = step ( hDec, receivedSignal );

    if counter == 3
        %
        display ( counter );

        %
        display ( data );

        %
        display ( encodedData );

        %
        display ( receivedSignal );

        %
        display ( receivedBits );
    end
end

%some of the outbut: % data 1 0 0 1 1 0 1 1 1 0 0 1 0 1 % 0 1 1 1 0 1 0 1 1 1 1 0 1 0 1 % 0

% encodedData = 0 0 0 1 0 1 1 0 1 1 1 1 0 % 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 % 1 0 0 0 1 1 0 1 1 1 0 0 0 0 1 % 0 0 0 0 1 0 0 0 1 1 0 1 1 1 0 1 1 % receivedSignal 1 1 1 -1 1 -1 -1 1 -1 -1 -1 -1 % 1 1 -1 1 -1 -1 1 1 -1 -1 1 -1 1 1 -1 % 1 -1 1 1 1 -1 -1 1 -1 -1 -1 1 1 1 1 % -1 1 1 1 1 -1 1 1 1 -1 -1 1 -1 -1 -1 % 1 -1 -1

Answer 1

[Babiker Abdallah]

sorry; I forgot the wrong output: resceivedBits = 1 0 0 1 0 1 1 0 1 0 0 1 1 0 1 0 1 1 0 1 1 0 1 0 1 1 0 1 0 1

errors is about 50%