• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37A no.11
• /
• pp.972-978
• /
• 2012

LDPC (low density parity check) code shows near Shannon limit performance by iterative decoding based on sum-product algorithm (SPA). Message updating procedure between variable and check nodes in SPA is done by a scheduling method. LDPC code shows different performance according to scheduling schemes. The conventional researches have been shown that the shuffled BP (belief propagation) algorithm shows better performance than the standard BP algorithm although it needs less number of iterations. However the reason is not analyzed clearly. Therefore the reason of difference in performance according to LDPC decoding algorithms is analyzed in this paper. 4 cases according to satisfaction of parity check condition are considered and compared. As results, the difference in the updating procedure in a cycle in the parity check matrix is considered to be the main reason of performance difference.

• Journal of Communications and Networks
• /
• v.17 no.4
• /
• pp.346-350
• /
• 2015

It is known that the progressive edge-growth (PEG) algorithm can be used to construct low-density parity-check (LDPC) codes at finite code lengths with large girths through the establishment of edges between variable and check nodes in an edge-by-edge manner. In [1], the authors derived a class of LDPC codes for relay communication systems by extending the full-diversity root-LDPC code. However, the submatrices of the parity-check matrix H corresponding to this code were constructed separately; thus, the girth of H was not optimized. To solve this problem, this paper proposes a modified PEG algorithm for use in the design of large girth and full-diversity LDPC codes. Simulation results indicated that the LDPC codes constructed using the modified PEG algorithm exhibited a more favorable frame error rate performance than did codes proposed in [1] over block-fading channels.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.7C
• /
• pp.587-593
• /
• 2010

In this paper we design an irregular low-density parity-check (LDPC) code for multiple-input multiple-output (MIMO) system, using a simple extrinsic information transfer (EXIT) chart method. The MIMO systems considered are optimal maximum a posteriori probability (MAP) detector. The MIMO detector and the LDPC decoder exchange soft information and form a turbo iterative receiver. The EXIT charts are used to obtain the edge degree distribution of the irregular LDPC code which is optimized for the MIMO detector. It is shown that the performance of the designed LDPC code is better than that of conventional LDPC code which was optimized for either the Additive White Gaussian Noise (AWGN) channel or the MIMO channel.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.41 no.9
• /
• pp.1095-1102
• /
• 2016

In this paper, we propose a decoding scheme that can apply to a three dimensional turbo product code(TPC) with a single parity check code(SPC). In general, SPC is used an axis with shortest code length in order to maximize a code rate of the TPC. However, SPC does not have any error correcting capability, therefore, the error correcting capability of the three-dimensional TPC results in little improvement in comparison with the two-dimensional TPC. We propose two schemes to improve performance of three dimensional TPC decoder. One is $min^*$-sum algorithm that has advantages for low complexity implementation compared to Chase-Pyndiah algorithm. The other is a modified serial iterative decoding scheme for high performance. In addition, the simulation results for the proposed scheme are shown and compared with the conventional scheme. Finally, we introduce some practical considerations for hardware implementation.

• ETRI Journal
• /
• v.45 no.3
• /
• pp.404-417
• /
• 2023

This paper proposed a novel method for constructing quasi-cyclic low-density parity-check (QC-LDPC) codes of medium to high code rates that can be applied in cloud data storage systems, requiring better error correction capabilities. The novelty of this method lies in the construction of sparse base matrices, using a girth greater than 4 that can then be expanded with a lift factor to produce high code rate QC-LDPC codes. Investigations revealed that the proposed large-sized QC-LDPC codes with high code rates displayed low encoding complexities and provided a low bit error rate (BER) of 10^-10 at 3.5 dB E_b/N₀ than conventional LDPC codes, which showed a BER of 10^-7 at 3 dB E_b/N₀. Subsequently, implementation of the proposed QC-LDPC code in a softwaredefined radio, using the NI USRP 2920 hardware platform, was conducted. As a result, a BER of 10^-6 at 4.2 dB E_b/N₀ was achieved. Then, the performance of the proposed codes based on their encoding-decoding speeds and storage overhead was investigated when applied to a cloud data storage (GCP). Our results revealed that the proposed codes required much less time for encoding and decoding (of data files having a 10 MB size) and produced less storage overhead than the conventional LDPC and Reed-Solomon codes.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.4C
• /
• pp.310-317
• /
• 2006

In this paper, we propose a new sequential message-passing decoding algorithm of low-density parity-check (LDPC) codes by partitioning check nodes. This new decoding algorithm shows better bit error rate(BER) performance than that of the conventional message-passing decoding algorithm, especially for small number of iterations. Analytical results tell us that as the number of partitioned subsets of check nodes increases, the BER performance becomes better. We also derive the recursive equations for mean values of messages at variable nodes by using density evolution with Gaussian approximation. Simulation results also confirm the analytical results.

• Proceedings of the IEEK Conference
• /
• 2004.08c
• /
• pp.473-476
• /
• 2004

Low-Density Parity-Check (LDPC) codes are recently emerged due to its excellent performance to use. However, the parity check matrices (H) of the previous works are not adequate for hardware implementation of encoders or decoders. This paper proposes a hybrid parity check matrix for partially parallel decoder structures, which is efficient in hardware implementation of both decoders and encoders. Using proposed methods, the encoding design can become practical while keeping the hardware complexity of partially parallel decoder structures.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.47 no.11
• /
• pp.36-42
• /
• 2010

This paper presents a hybrid approach to the construction of quasi-cyclic (QC) low-density parity-check (LDPC) codes based on parallel bundles in Euclidean geometries and circulant permutation matrices. Codes constructed by this method are shown to be regular with large girth and low density. Simulation results show that these codes perform very well with iterative decoding and achieve reasonably large coding gains over uncoded system.

• Proceedings of the IEEK Conference
• /
• 2008.06a
• /
• pp.161-162
• /
• 2008

In this paper we design an irregular low-density parity-check (LDPC) code for a multi-input multi-output (MIMO) system. The considered MIMO system is minimum mean square error soft-interference cancellation (MMSE-SIC) detector. The MMSE-SIC detector and the LDPC decoder exchange soft information and consist a turbo iterative detection and decoding receiver. Extrinsic information transfer (EXIT) charts are used to obtain the edge degree distribution of the irregular LDPC code which is optimized for the input-output transfer chart of the MMSE-SIC detector. It is shown that the performance of the designed LDPC code is much better than that of conventional LDPC code optimized for the AWGN channel.

• Proceedings of the IEEK Conference
• /
• 2002.06a
• /
• pp.323-326
• /
• 2002

In this paper, we study the improved bounds on the performance of low-density parity-check (LDPC) codes over binary-input additive white Gaussian noise (AWGN) channels with belief propagation (BP) decoding in log domain. We define an extended Gallager ensemble based on a new method of constructing parity check matrix and make use of this way to improve upper bound of LDPC codes. At the same time, many simulation results are presented in this paper. These results indicate the extended Gallager ensembles based on Hamming codes have typical minimum distance ratio, which is very close to the asymptotic Gilbert Varshamov bound and the superior performance which is better than the original Gallager ensembles.