Decoding Complexity and Performance of Short-Block LDPC Codes Over GF(q)

M Kurkoski Brian, Kazuhiko Yamaguchi, Kingo Kobayashi

Xin Chen, Aidong Men

Low-density parity-check (LDPC) codes over finite fields GF(q) have a better performance than those of the binary low-density parity-check codes, at short and medium block lengths, but the decoder of GF(q)-LDPC has more complexity. In this paper, we present a new reduced-complexity belief propagation (BP) decoding algorithm for GF(q)-LDPC codes by analyzing the reliability of code symbols. Instead of update all the variable nodes during iteration, we just update variable nodes which are mostly to be in an error. The algorithm also shows a property to reduce the effects of oscillating on decoding. The simulations prove that we could improve performance and reduce complexity at the same time for short and medium GF(q)-LDPC codes.

M Kurkoski Brian, Kazuhiko Yamaguchi, Kingo Kobayashi

Xin Chen, Aidong Men, Wei Zhou

Nonbinary low-density parity-check (LDPC) codes over finite fields GF(q) have a better performance than those of the binary low-density parity-check codes, at short and medium block lengths, but the decoder of GF(q)-LDPC has more complexity. In this paper, a new stopping criterion is proposed. Based on the changes of the variance of variable node¿s extrinsic information, the criterion can predict a decoding failure and decide whether the iteration of the decoder should be stopped. The simulation results show that the stopping criterion can greatly reduces the average number of required iterations of GF(q)-LDPC decoder with negligible performance loss.

Jigisha N. Patel, Neeta Chapatwala, Mrugesh Patel

Low Density Parity Check (LDPC) codes have excellent error correcting performance. LDPC codes are one of the block coding techniques and it performs near Shannon limit and recommended for many practical applications. Non-binary LDPC codes extension of binary LDPC in error correcting property especially for short and moderate block length. In many digital communication systems these codes have strong competitors of turbo codes for error control. Low Density Parity Check as it name is suggests that in a parity check matrix (H) consists of very small number of non-zero elements comparing with zero elements. The strength of the LDPC code defines Parity Check Matrix (PCM). LDPC code contains two types of decoding algorithms hard and soft decision algorithm. By comparing with other traditional decoding algorithm FFT based sum product algorithm reduced computation complexity with better decoding performance. In this paper, LDPC codes for FFT based sum product decoding algorithm performances are analysed for various order of Galois Field GF(q) using AWGN channel. Decoding performance measured in terms of symbol error rate which improve with increasing order of Galois field.

Xiu-Cheng Zheng, Francis C. M. Lau, Chi Kong Tse