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Integer programming-based non-uniform window decoding schedules for spatially coupled low-density parity-check codes
(2022-10-01)
Khittiwitchayakul, Sirawit
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Phakphisut, Watid
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Supnithi, Pornchai
Spatially coupled low-density parity-check (SC-LDPC) codes generally use a window decoding scheme, which is known to yield a near-optimal decoding, compared to full block decoding. Recently, a non-uniform schedule has been proposed to eliminate unnecessary updates of variable nodes within a window: this schedule is generated based on the behaviour of variable node updates analysed by density evolution. Here, the authors present a new non-uniform schedule based on integer programming, whereby the objective functions and constraints are derived from a protograph-based extrinsic information transfer chart. Our design is more flexible than the previous design, because the integer programming-based design allows reduction of update numbers and performance losses through the constraints function, whereas the previous design requires observation of variable node update behaviour. The authors report the performance of their designs of non-uniform schedules in additive white Gaussian noise (AWGN) and inter-symbol interference (ISI) channels. Particularly, in the ISI channel, the authors’ non-uniform schedules are designed with cooperative decoding between a Bahl-Cocke-Jelinek-Raviv (BCJR) detector and an SC-LDPC decoder.
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Associated Sectors of Magnetic Recording Systems Using Spatially Coupled LDPC Codes
(2022-02-18)
Khittiwitchayakul, Sirawit
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Phakphisut, Watid
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Supnithi, Pornchai
In traditional magnetic recording systems, nonassociated sectors are mainly adopted, whereby two consecutive sectors are decoded independently by the low-density parity-check (LDPC) codes. In this paper, we propose a magnetic recording system with associated sectors, constructed using spatially coupled low-density parity-check (SC-LDPC) codes. If the SC-LDPC decoder cannot correct the erroneous bits in the current sector, it can request information stored in previous sectors to improve decoding performance. Moreover, we modify protograph-based extrinsic information transfer (P-EXIT) charts to examine the theoretical performance of SC-LDPC codes applied to both non-associated and associated sectors. Our theoretical results show that the associated sectors achieve significant performance gains compared to the traditional non-associated sectors.
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Reliability Ratio-Based Serial Algorithm of LDPC Decoder for Turbo Equalization Schemes
(2022-02-01)
Khittiwitchayakul, Sirawit
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Phakphisut, Watid
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Supnithi, Pornchai
Serial decoding algorithms of low-density parity-check (LDPC) code converge efficiently with low errors. Previously, a serial decoding algorithm, named a shuffled belief-propagation (SBP), was applied in turbo equalization of bit-patterned magnetic recording (BPMR) systems. With the SBP algorithm, an LDPC decoder converged twice as fast as one using conventional BP algorithms. We further improved the convergence speed of SBP by updating the messages in an adaptive order, which played a flexible role throughout decoding. We proposed two adaptive-serial algorithms for LDPC codes in turbo equalization. One updated the messages using the extrinsic loglikelihood ratio (LLR) and the result of the parity-check equation checking. The second contained an additional rule that tracked the LLR sign changes in each iteration. Both algorithms converged faster and with lower bit error rates (BERs) than the SBP and previous adaptive-serial algorithms in a BPMR system with media noise.
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Sliding-Window Turbo Equalization and Its Reduced-Complexity Decoding Techniques
(2022-01-01)
Khittiwitchayakul, Sirawit
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Phakphisut, Watid
Turbo equalization is a cooperative error-correcting approach to achieve a target bit-error rate over inter-symbol interference channels. In this paper, we proposed a new turbo equalization, called sliding-window turbo equalization (SW-TE), consisting of the Bahl-Cocke-Jelinek-Raviv detector and a spatially coupled, low-density, parity-check decoder. Moreover, the Protograph-based Extrinsic Information Transfer (P-EXIT) chart was modified to investigate the asymptotic behavior of SW-TE. Our analyses showed that SW-TE outperformed conventional turbo equalization in terms of decoding threshold. Based on the P-EXIT chart analysis, we further proposed a guideline of the reduced-complexity decoding techniques for SW-TE, eliminating unnecessary branch metric updates during turbo iterative decoding. Our simulations corroborated the analytical results, showing that SW-TE outperformed conventional turbo equalization while maintaining an acceptable level of complexity.
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Development of 5G LDPC Experimental Kit
(2022-01-01)
Srisupha, Thanat
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Mueadkhunthod, Krittiyaporn
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Phakphisut, Watid
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Khittiwitchayakul, Sirawit
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Puntsri, Kidsanapong
In this work, we develop the 5G LDPC experimental kit to demonstrate the encoding processes of LDPC codes in 5G new radio. The experimental kit consists of a graphical user interface (GUI) and an FPGA development board. Any parameters defined in the 5G new radio can be configured and their encoding results are presented in the GUI. We also develop the 5G LDPC encoder as the software module integrated within the GUI. The user can select the software or hardware for the 5G LDPC encoder. The experimental kit is simple to use and no need any complicated setups. We believe that the experimental kit would be useful to anyone interested in the LDPC 5G NR standard.
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Associated sectors of magnetic recording system via spatially coupled LDPC codes
(2021-05-19)
Khittiwitchayakul, Sirawit
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Supnithi, Pornchai
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Phakphisut, Watid
Spatially coupled low-density parity-check (SC- LDPC) codes have emerged as promising advanced error- correcting codes (ECC) for future high-density magnetic recording (MR) systems, which require excellent error-correcting performance and acceptable practical complexity. In the traditional MR systems, the non-associated sectors are generally used, whereby two consecutive sectors are independently decoded by ECC. In this work, we propose the associated sectors of MR systems in which the information stored in the previous sectors can be requested by ECC to reinforce the decoding of the current sector. Moreover, the proposed associated sectors can mitigate the rate-loss problem of SC-LDPC codes in the MR systems. We demonstrate the bit-error-rates (BERs) of SC-LDPC codes in the bit-patterned media magnetic recording (BPMR) systems with non-associated sectors and associated sectors. The simulation results show that the associated sectors help achieve significant performance gains compared to the non-associated sectors.
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EXIT Chart Analysis of Protograph-based LDPC Codes for Unequal Power Two-User Gaussian Multiple Access Channel
(2020-07-01)
Khittiwitchayakul, Sirawit
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Phakphisut, Watid
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Supnithi, Pornchai
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Min Myint, Lin Min
In this work, we analyze the theoretical performances of protograph-based LDPC codes for unequal power two-user Gaussian multiple access channel (GMAC) by using Extrinsic information transfer (EXIT) chart. We show that the decoding performances of LDPC codes for two-users are improved significantly when the transmitted power of user increases. Moreover, we present the design of protograph structures of the LDPC codes for unequal power two-user GMAC by using the differential evolution (DE). The results show that the designed LDPC codes outperform the traditional LDPC codes.
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EXIT Chart Analysis of Serial Window Decoding of SC-LDPC codes
(2019-06-01)
Khittiwitchayakul, Sirawit
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Phakphisut, Watid
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Supnithi, Pornchai
Spatially coupled low-density parity-check (SC-LDPC) codes can be decoded by a sliding window which can provide the lower complexity and latency than that of underlying LDPC block code (LDPC-BC) decoding. In this work, we propose to use an Extrinsic Information Transfer (EXIT) chart as an analysis tool for the window decoding of SC-LDPC code. Herein, the EXIT chart analysis is applied for both window decoding strategies like flooding and serial strategies. The analysis results show that the window decoding with serial strategy can converge faster than that of flooding strategy. The required numbers of decoding iteration can be reduced greatly without the performance degradations.
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Sliding-window processing of turbo equalization for partial response channels
(2019-04-01)
Khittiwitchayakul, Sirawit
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Phakphisut, Watid
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Supnithi, Pornchai
Spatially coupled low-density parity-check (SC-LDPC) codes are the attractive candidates for the application requiring a practical constraint on the latency and complexity. In previous works, the turbo equalization consisting the SC-LDPC window decoder and Bahl-Cocke-Jelinek-Raviv (BCJR) detector is used to tackle the inter-symbol interferences (ISIs) in the magnetic recording systems. However, the prior works consider only the SC-LDPC codes which replace the conventional LDPC block codes. In this work, we propose the modification of turbo equalization processing whereby both the SC-LDPC decoder and BCJR detector operate using the sliding window. The results show that the proposed turbo equalization schemes used in the partial response (PR) channel can provide better bit error rate (BER) performances than the conventional turbo equalization.
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Reduced Complexity Window Decoding of Spatially Coupled LDPC Codes for Magnetic Recording Systems
(2018-11-01)
Khittiwitchayakul, Sirawit
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Phakphisut, Watid
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Supnithi, Pornchai
Spatially coupled low-density parity-check (SC-LDPC) codes have emerged to possess capacity-approaching performance. The SC-LDPC codes can be decoded by a sliding window, therefore, the decoding latency and complexity of SC-LDPC codes are lower than those of underlying LDPC codes when the codeword length is very large. In this paper, the SC-LDPC decoder with the sliding window is employed in turbo equalization of magnetic recording systems. We examine the bit error rates (BERs) of the output of the sliding window during the iterative decoding, and then observe that the consecutive code blocks have approximately the same BERs. Herein, to reduce decoding complexity of SC-LDPC codes, the consecutive code blocks can be considered as the output of SC-LDPC codes. In addition, the non-uniform schedule update is adopted in the window decoding to avoid unnecessary updates within a window. The simulation results show that the proposed decoding algorithms applied in bit-patterned media magnetic recording systems can achieve a significant reduction in complexity compared to the traditional decoding without any loss in BER performance.

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