Warisarn, Chanon

Preferred name

Warisarn, Chanon

Alternative Name

Warisarn, C.

Main Affiliation

Integrated Innovative Technology

chanon.wa@kmitl.ac.th

Now showing 1 - 10 of 104

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A Soft ITI Mitigation Method for Coded 2H2T BPMR Systems
(2019-06-01)
Koonkarnkhai, Santi
;
Warisarn, Chanon
;
Chirdchoo, Nitthita
;
Kovintavewat, Piya
To achieve an areal density (AD) of hard disk drives (HDDs) up to 4 Tb/in<sup>2</sup>, a bit-patterned magnetic recording (BPMR) system is one of the interesting candidates for the emerging magnetic recording technologies. Generally, intertrack interference (ITI) is a major problem for the BPMR system and it can deteriorate the overall system performance. Thus, this paper proposes the soft ITI mitigation method for coded two-head two-track (2H2T) BPMR systems. Specifically, the proposed method subtracts the estimated ITI signal (generated based on the soft decision obtained from a decoder for each turbo iteration) from the original readback signal during the turbo decoding process. Simulation results show that the proposed method outperforms the conventional method employing the hard decision to estimate the ITI signal at 2 and 2.5 Tb/in<sup>2</sup>.
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Reliability Test Techniques in Tabu Search Detection for Enhancing BER Performance of Array Reader Bit-Patterned Magnetic Recording Systems
(2026-01-01)
Mattayakan, Mutita
;
Rueangnetr, Natthakan
;
Kankhunthod, Kittipon
;
Warisarn, Chanon
Bit-patterned magnetic recording (BPMR) at ultra-high densities is strongly affected by inter-track interference (ITI). To cope with severe ITI, we introduce a reliability-testing mechanism with adaptive symmetric thresholding based on the distribution of log-likelihood ratios (LLRs) to effectively identify unreliable bits while controlling the computational complexity of the Tabu search (TS) detector. Additionally, the selected bits identified from the TS detection are employed to refine the original LLR values through a proposed soft-information adjustment (SIA) process. Moreover, we also present an LLR weighting scheme to further enhance the refined LLRs produced by the SIA process, thereby improving the performance of low-density parity-check decoding. Results indicate that our proposed technique can reduce the complexity of the TS detector by using a reliability-testing mechanism. The SIA can be effectively combined with an LLR weighting scheme, thereby improving bit-error rate performance over conventional BPMR systems.
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Bi-directional timing recovery for magnetic recording systems
(2009-12-01)
Warisarn, Chanon
;
Supnithi, Pornchai
;
Kovintavewat, Piya
Magnetic recording systems employ conventional timing recovery to synchronize the sampler with the readback signal. However, conventional timing recovery does not perform well when the timing error is large. This paper proposes the bidirectional timing recovery, which utilizes conventional timing recovery to sample the readback signal both in forward direction and in backward direction. The outputs of these two operations are averaged and sent them to the Viterbi detector to determine the most likely input sequence. Results indicate that the bidirectional timing recovery performs better than conventional timing recovery, especially when the timing error is large. ©2009 IEEE.
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A study of multiple reads of target track prior to detection for two-dimensional magnetic recording
(2015-07-14)
Singhaudom, W.
;
Supnithi, P.
;
Warisarn, C.
Two-dimensional magnetic recording (TDMR) has recently received wide attention as a good candidate for next generation high-density data storage [1]. However, the read-back signal is subject to the combination of inter-track interference (ITI) and inter-symbol interference (ISI). Therefore, a major challenge to apply TDMR depends on the development of two-dimensional signal processing. It is widely studied in a variety of forms, leading to the compromise between detection performance and computation complexity. Some recent works on TDMR channels are presented in [2]-[4]. In [2], performance is enlarged by using 2D iterative detector. As for [3] and [4], multiple readbacks from array-reader were proposed to detect data bit.
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Soft-output decoding of 2D modulation codes for bit-patterned media recording
(2015-07-14)
Warisarn, C.
;
Kovintavewat, P.
The two-dimensional (2D) interference is a major impairment in bit-patterned media recording (BPMR) systems because of small bit and track pitches, especially at high recording densities [1]. To mitigate this problem, we introduced 2D modulation codes [2-3], which output only the hard decision, for an uncoded BPMR system (i.e., without error-correction codes). To utilize a rate-4/5 constructive inter-track interference (CITI) code [2] in the coded BPMR system, which employs a low-density parity-check (LDPC) code, we propose the log-likelihood ratio (LLR) algebra implementation in Boolean logic mappings for the CITI coding scheme. Then, this soft CITI coding scheme together with a modified 2D soft-output Viterbi algorithm (2D-SOVA) detector [4] and a LDPC decoder will jointly perform iterative decoding.
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Track Mis-registration Correction Method in Two-Head Two-Track BPMR Systems
(2020-06-01)
Kankhunthod, Kittipon
;
Busyatras, Wiparat
;
Warisarn, Chanon
One of the main problems in a Bit-patterned media recording (BPMR) system at an ultra-high areal density is the effect of track mis-registration (TMR), which can severely degrade the system's performance. Practically, the TMR effect is controlled by the servo system. That requires some areas of record to store redundancy bits. In this paper, we propose a simple linear energy ratio finding (SLERF) technique using only the two readback signals for estimating the TMR level in two- head/two-track (2H2T) BPMR systems, which unrequired the extravagant redundancy bits. Next, we utilize the appropriate equalizers, which are accordingly designed with the estimated TMR levels, to correct the TMR effect. Moreover, we also propose a soft-information adjustment (SIA) technique that operates after obtaining the soft-information from the two-dimensional soft-output Viterbi algorithm (2D-SOVA) detectors in order to improve the bit error rate (BER) performance of recording systems. Computer simulation reveals that the SLERF and SIA techniques can impressively estimate the TMR levels and further effectively correct the TMR effect as well, respectively. Therefore, it leads to obtaining better BER performance in particular where the system is impaired by position jitter noise.
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A TMR mitigation method with 3-track data detection for multi-track multi-head BPMR system
(2017-08-10)
Warisarn, C.
;
Busyatras, W.
;
Myint, L. M.
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Koonkarnkhai, S.
;
Kovintavewat, P.
An off-track situation from misalignment between the center of read head and that of target track is also known as track mis-registration (TMR), which is one of major problems in bit-patterned media recording (BPMR), especially at high areal density (AD) [1-4].
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Investigation of writing error in staggered heated-dot magnetic recording systems
(2017-05-01)
Tipcharoen, W.
;
Warisarn, C.
;
Tongsomporn, D.
;
Karns, D.
;
Kovintavewat, P.
To achieve an ultra-high storage capacity, heated-dot magnetic recording (HDMR) has been proposed, which heats a bit-patterned medium before recording data. Generally, an error during the HDMR writing process comes from several sources; however, we only investigate the effects of staggered island arrangement, island size fluctuation caused by imperfect fabrication, and main pole position fluctuation. Simulation results demonstrate that a writing error can be minimized by using a staggered array (hexagonal lattice) instead of a square array. Under the effect of main pole position fluctuation, the writing error is higher than the system without main pole position fluctuation. Finally, we found that the error percentage can drop below 10% when the island size is 8.5 nm and the standard deviation of the island size is 1 nm in the absence of main pole jitter.
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A simple recorded-bit patterning scheme for bit-patterned media recording
(2013-09-02)
Arrayangkool, Autthasith
;
Warisarn, Chanon
;
Myint, Lin M.M.
;
Kovintavewat, Piya
In bit-patterned magnetic recording (BPMR), inter-symbol interference (ISI) and inter-track interference (ITI) become a major impairment due to small bit and track pitches. One way to alleviate ISI and ITI is to encode the data sequence before recording. In general, two-dimensional (2D) coding scheme requires many redundant bits, thus lowering the code rate. This paper proposes a novel 2D coding scheme (referred to as a simple recorded-bit patterning (RBP) scheme) with high code rate to combat both ISI and ITI effects. Specifically, the data bits will first be patterned by finding the best data pattern based on a look-up table that can avoid severe ISI and ITI effects before recording. Simulation results indicate that the proposed scheme can provide a significant performance improvement if compared to the system without coding. © 2013 IEEE.
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Read-reference BER categorization improvement in WPOH measurement of HAMR drive
(2018-07-02)
Jariampan, Panadda
;
Warisarn, Chanon
Bit-error rate (BER) is used as a primary metric in write power-on hours (wPOH) measurement of heat-assisted magnetic recording (HAMR) drive. BER is measured after writing process represented writing quality while read-only BER showed reading quality or read reference in the measurement. The read-reference BER usually remains close to its initial value, however, in some cases it shows BER fluctuation or degradation as well. Therefore, in this paper focuses on the read-reference BER categorization and an improvement of the categorization algorithm.

Warisarn, Chanon

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