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Decoding Algorithms Based on Oscillation for LowDensity Parity Check Codes
Satoshi GOUNAI Tomoaki OHTSUKI
Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Vol.E88A
No.8
pp.22162226 Publication Date: 2005/08/01
Online ISSN:
DOI: 10.1093/ietfec/e88a.8.2216
Print ISSN: 09168508 Type of Manuscript: PAPER Category: Coding Theory Keyword: lowdensity paritycheck code, log likelihood ratio belief propagation, ordered statistic decoding, oscillation,
Full Text: PDF(667.4KB)>>
Summary:
In this paper we focus on the decoding error of the LogLikelihood Ratio Belief Propagation (LLRBP) decoding algorithm caused by oscillation. The decoding error caused by the oscillation is dominant in high E_{b}/N_{0} region. Oscillation of the LLR of the extrinsic value in the bit node process (exLLR) is propagated to the other bits and affects the whole decoding. The Ordered Statistic Decoding (OSD) algorithm is known to improve the error rate performance of the LLRBP decoding algorithm. The OSD algorithm is performed by deciding the reliability of each bit based on a posteriori probability. In this paper we propose two decoding algorithms based on two types of oscillations of LLR for LDPC codes. One is the oscillationbased OSD algorithm with deciding the reliability of each bit based on oscillation. The other is the oscillationbased LLRBP decoding algorithm that modifies exLLR based on oscillation. In the oscillationbased LLRBP decoding algorithm, when exLLR oscillates, then we reduce the magnitude of this exLLR to reduce the effects on the other bits. Both algorithms improve the decoding errors caused by oscillation. From the computer simulations, we show that paying attention to the oscillation, we can improve the error rate performance of the LLRBP decoding algorithm.

