Low-Floor Detection/Decoding of LDPC-Coded Partial Response Channels

The error-rate floor phenomenon associated with iterative LDPC decoders has delayed the use of LDPC codes in certain communication and storage systems. Error floors are known to generally be caused by so-called trapping sets which have the effect of confounding the decoder. In this paper, we introdu...

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Bibliographic Details
Published in:IEEE journal on selected areas in communications 2010-02, Vol.28 (2), p.252-260
Main Authors: Han, Yang, Ryan, William E.
Format: Article
Language:English
Subjects:
Acceleration
AWGN channels
bit pinning
Channels
Computational modeling
Decoders
Decoding
Delay
error floor
Errors
Importance sampling
Iterative decoding
LDPC codes
Maximum likelihood decoding
Monte Carlo methods
Parity check codes
Partial response channels
Rest
Simulation
Trapping
trapping sets
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Summary:The error-rate floor phenomenon associated with iterative LDPC decoders has delayed the use of LDPC codes in certain communication and storage systems. Error floors are known to generally be caused by so-called trapping sets which have the effect of confounding the decoder. In this paper, we introduce two techniques that lower the error-rate floors for LDPC-coded partial response (PR) channels which are applicable to magnetic and optical storage. The techniques involve, via external measures, "pinning" one of the bits in each problematic trapping set and then letting the iterative decoder proceed to correct the rest of the bits. We also extend our earlier work on generalized-LDPC (G-LDPC) decoders for error-floor mitigation on the AWGN channel to partial response channels. Our simulations on PR1 and EPR4 channels demonstrate that the floor for the code chosen for this study, a 0.78(2048,1600) quasicyclic LDPC code, is lowered by orders of magnitude, beyond the reach of simulations. Because simulation in the floor region is so time-consuming, a method for accelerating such simulations is essential for research in this area. In this paper, we present an extension of Richardson's importance sampling technique for estimating the level of error floors.
ISSN:0733-8716
1558-0008
DOI:10.1109/JSAC.2010.100214