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IEEE Wireless Communications and Networking Conference

A Perturbation Method for Decoding LDPC Concatenated with CRC

Dongliang Xiao, Jianhua Lü, Chunlei Lin, Bingli Jiao

Published Mar 1, 2007• 9 citations
Publisher

Abstract

In this paper, a novel decoding algorithm using perturbation techniques for LDPC concatenated with CRC (LDPC-CRC) is proposed. The CRC is used to check the residual error of the BP algorithm, while a new parameter is introduced to LDPC decoding to describe the reliability of each bit in the iterative decoding algorithm. Upon an error is detected, re-decoding process with perturbation method will be aroused. Simulation results show that this method lowers the error floor for codeword length of several hundred bits effectively.

DOI
10.1109/wcnc.2007.128

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In this paper, a novel decoding algorithm using perturbation techniques for LDPC concatenated with CRC (LDPC-CRC) is proposed. The CRC is used to check the residual error of the BP algorithm, while a new parameter is introduced to LDPC decoding to describe the reliability of each bit in the iterative decoding algorithm. Upon an error is detected, re-decoding process with perturbation method will be aroused. Simulation results show that this method lowers the error floor for codeword length of several hundred bits effectively.
In modern communication systems, the concatenation of a low-density parity-check (LDPC) code with a cyclic redundancy check (CRC) code is commonly used for error correction. In this paper, we propose a low-complexity two-stage scheme for decoding these codes using their concatenation structures. In the first stage, the traditional belief propagation (BP)-based iterative algorithm with a relative small maximum number of iterations is performed for decoding the LDPC code. If an LDPC codeword is obtained in this stage, the decoding process terminates. Otherwise, the second stage of the decoding process is performed, in which the guessing random additive noise decoding (GRAND) algorithm is applied to the CRC code. A list of information sequences satisfying the CRC check is obtained, each of which is then encoded to an LDPC codeword. The most likely codeword among them is the output of the decoding approach. The simulation results indicate that the proposed two-stage decoding approach can outperform the traditional BP-based iterative algorithm with a large maximum number of iterations. Moreover, the average complexity of the proposed approach is relatively low.
In this paper, a fresh belief propagation (BP) decoding algorithm is proposed. The proposed decoding algorithm with improved perturbation method is designed for short length low density parity-check (LDPC) codes aided by cyclic redundancy check (CRC). In the proposed algorithm corresponding to path size L, L decoding paths are considered concurrently. Then, a single codeword is selected according to the checking results of CRC. Simulation results show that the modified CRC-aided decoding scheme can enhance the error-correcting performance of short LDPC codes effectively.
The dynamic perturbation (DP) decoding algorithm of Cyclic Redundancy Check (CRC) concatenated polar codes over Additive White Gaussian Noise (AWGN) channel is proposed. CRC concatenated polar codes append the CRC bits at the end of information bits and then feeds the resulting vector as input to the polar encoder. This paper improves the CRC-aided decoding method of polar codes based on perturbation, and proposes a dynamic perturbation decoding method for Polar-CRC concatenation code by controlling the interference noise dynamically. The proposed dynamic perturbation decoding is better than the original method with successive cancellation (SC) decoding.
Despite the performance of 5th Generation Low Density Parity Check (5G-LDPC) codes close to the capacity limit, the near-optimal floating-point BP decoding will lead to excessive use of hardware and high complexity of calculation. Thus, the quantized min-sum decoder with limited-precision is usually used in practical implementations. No matter using high or low precision quantization, some 5G-LDPC codes always suffer from the problem of high error floor, which affects their applications in future ultra-reliable scenarios. Using Reed-Solomon (RS) codes as the outer codes can significantly lower the error floor of 5G-LDPC codes due to their Hamming distance properties and excellent error-correction capability. In order to further improve the overall performance, an efficient iterative decoding algorithm of RS-LDPC concatenated codes is proposed in this paper. The proposed iterative algorithm of RS-LDPC codes can achieve noticeable gains over the 5G-LDPC codes at lower FER.
Error floor properties of low-density parity-check(LDPC)codes using different decoding algorithms were statistically analyzed utilizing test data from a hardware evaluation platform.The analysis shows that the number of residual error bits in an error codeword after decoding failure using the sum-product(SP)algorithm or the modified min-sum(MMS)algorithm is usually quite small;therefore,LDPC codes can serve as the inner code in a concatenated coding system to achieve an ultra low bit error rate.The analysis also shows that SP algorithm is more suitable for a concatenated coding system than MMS algorithm since less residual error bits occur when using the SP algorithm.Concatenated codes based on the analysis achieve bit error rates lower than 10-10 with a low decoding threshold.