Modified belief propagation decoding algorithm for low-density parity check code based on oscillation

Satoshi Gounai, Tomoaki Ohtsuki, Toshinobu Kaneko

Research output: Chapter in Book/Report/Conference proceedingConference contribution

16 Citations (Scopus)

Abstract

A Low-Density Parity Check (LDPC) code with the Belief Propagation (BP) or the Log-Likelihood Ratio Belief Propagation (LLR-BP) can achieve good Bit Error Rate (BER) performance approaching the Shannon limit. When a parity check matrix of the LDPC code has the cycle, the BP and LLR-BP decoding algorithms achieve approximate Maximum A posterior Probability (MAP) decoding. Although the decoding algorithms are approximate MAP decoding, LDPC codes can achieve very good BER. For the short and middle length LDPC codes, BER and BLock Error Rate (BLER) performances are affected by cycle largely. In each iteration, the magnitudes of a posterior LLRs of some bits oscillate owing to cycles. The oscillation is the dominant error factor in the high Eb/N0 region for short and middle length LDPC codes. In this paper, we extend the definition of oscillation to extrinsic LLR (ex-LLR) derived in the bit node process and propose the modified LLR-BP and the modified UMP-BP decoding algorithms. To reduce effects of oscillating ex-LLRs on decoding, for oscillating ex-LLRs, we add the previous ex-LLR to the current ex-LLR. From the computer simulation, we show that for short and middle length LDPC codes, with a simple modification, our proposed decoding algorithms can improve the conventional LLR-BP and UMP-BP decoding algorithms. In particular, we show that the modified UMP-BP decoding algorithm with low complexity can achieve better BER and BLER than the conventional LLR-BP decoding algorithm.

Original languageEnglish
Title of host publication2006 IEEE 63rd Vehicular Technology Conference, VTC 2006-Spring - Proceedings
Pages1467-1471
Number of pages5
Publication statusPublished - 2006 Dec 1
Event2006 IEEE 63rd Vehicular Technology Conference, VTC 2006-Spring - Melbourne, Australia
Duration: 2006 May 72006 Jul 10

Publication series

NameIEEE Vehicular Technology Conference
Volume3
ISSN (Print)1550-2252

Other

Other2006 IEEE 63rd Vehicular Technology Conference, VTC 2006-Spring
CountryAustralia
CityMelbourne
Period06/5/706/7/10

ASJC Scopus subject areas

  • Computer Science Applications
  • Electrical and Electronic Engineering
  • Applied Mathematics

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