TY - GEN

T1 - Modified belief propagation decoding algorithm for low-density parity check code based on oscillation

AU - Gounai, Satoshi

AU - Ohtsuki, Tomoaki

AU - Kaneko, Toshinobu

PY - 2006/12/1

Y1 - 2006/12/1

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=34047173063&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=34047173063&partnerID=8YFLogxK

M3 - Conference contribution

AN - SCOPUS:34047173063

SN - 0780393929

SN - 9780780393929

T3 - IEEE Vehicular Technology Conference

SP - 1467

EP - 1471

BT - 2006 IEEE 63rd Vehicular Technology Conference, VTC 2006-Spring - Proceedings

T2 - 2006 IEEE 63rd Vehicular Technology Conference, VTC 2006-Spring

Y2 - 7 May 2006 through 10 July 2006

ER -