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#126 Error for high SNR for Modulator_2d::demodulate_soft_bits

release_3.10.x
closed
5
2012-09-15
2006-03-22
Anonymous
No

Modulator_2d::demodulate_soft_bits does not work well
for high SNR. For high SNR value, it produces inf and
-inf, which generates error when channel decoding is
operate on the demodulated bits. I have change to
demodulate_soft_bits_approx and it works well then.

Regards,
Arthur.

Discussion

  • Erik G. Larsson

    Erik G. Larsson - 2006-08-09

    Logged In: YES
    user_id=1284695

    Arthur, Could you send us an example of code where you
    reproduce this error? On my system, I was able to set N0 to
    well below 1e-300 before the demodulator output was inifite
    (this infinity output seems to be caused by the 1/N0
    calculation) - note that such a low noise level is zero for
    all practical purposes. Possibly system dependent.

    Updated documentation to suggest Modulator_ND class be used
    instead -- faster and better numerical stability.

    Erik

     
  • Adam Piątyszek

    Adam Piątyszek - 2006-08-10

    Logged In: YES
    user_id=1004597

    Finally, we managed to solve the problem in Modulator_2d
    demodulate_soft_bits() function. The fix is already in the
    repository (rev. 599). See ChangeLog for more information.
    Closing this bug report.

    /ediap

     

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