Warisarn, Chanon

Preferred name

Warisarn, Chanon

Alternative Name

Warisarn, C.

Main Affiliation

Integrated Innovative Technology

chanon.wa@kmitl.ac.th

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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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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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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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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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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.
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Effect of hotspot position fluctuation to writing capability in heated-dot magnetic recording
(2016-07-01)
Tipcharoen, Warunee
;
Warisarn, Chanon
;
Kaewrawang, Arkom
;
Kovintavewat, Piya
This work presents the effect of hotspot position fluctuation to writing capability in heated-dot magnetic recording systems at an areal density (AD) beyond 2 Tbpsi via a micromagnetic modeling. At high ADs, the hotspot and the write field gradient may not be correctly focused on the target island because the bit islands are closely positioned to one another. This may lead to the overwriting/erasing of the previously written islands, which can severely affect the recording performance. Therefore, this work studies the 3-by-3 data patterns that easily cause an error when the hotspot and write head positions are fluctuated by various island pitches. Simulation results indicate that the data pattern that leads to the highest/ lowest error occurrence frequency is the one with the first, second and fourth islands having the opposite/same magnetization direction to/as the write field, regardless of the magnetization direction of the third island. This result can, for example, be utilized to design a two-dimensional modulation code to prevent such destructive data patterns, thus helping enhance the overall system performance.
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Neural Networks Input Techniques to Maintain a Small Skew Angle in Bit-Patterned Magnetic Recording with a V-Shaped Read-Head Array
(2023-01-01)
Fatika, Kirana Alif
;
Koonkarnkhai, Santi
;
Kovintavewat, Piya
;
Warisarn, Chanon
The demand for enormous storage devices has kept increasing, leading to the development of various advanced technologies with a vast storage capacity. Extensive numbers of related research studies have been aiming at optimizing code design and algorithms analytically; however, enacting them on practical devices has been scarce. Achieving this demand might bring some obstacles called two-dimensional interference and skew angle (SA). To meet the challenge of the obstacle, we propose a SA detection method for bit-patterned magnetic recording systems by computing a specific target by three readback sequences before estimating the SA value and detecting the SA amount happening in the system using an application of neural network namely multilayer perceptron. An error correction code, low-density parity-check, is applied, and its decoder outputs a log-likelihood ratio whose probability density distribution is examined. The simulation results show that the sliding window technique can significantly provide a better bit error rate performance.
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Multitrack reading scheme with single reader in BPMR systems
(2017-10-19)
Buajong, Chaiwat
;
Warisarn, Chanon
In ultra-high track density magnetic recording such as bit-patterned media recording (BPMR), the narrow track reader is required to avoid the strong intertrack interference (ITI). However, the reduction of reader size to the track pitch is considerably difficult. Therefore, this paper proposes to use the multitrack reading scheme with the staggered island BPMR. The effects of the island size and position fluctuation are investigated. Then, two-dimensional (2D) decoding scheme will be considered to mitigate the reader's narrow track width requirement by oversampling technique. Moreover, both the threshold and Partial Response Maximum Likelihood (PRML) detection were also examined the system performance. Simulation results indicate that the proposed system outperforms the conventional reading system, especially for high areal density.
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A simple inter-track interference subtraction technique in Bit-Patterned Media Recording (BPMR) systems
(2018-05-01)
Buajong, Chaiwat
;
Warisarn, Chanon
In this paper, we demonstrate how to subtract the intertrack interference (ITI) before the decoding process in multi-track multihead bit-patterned media recording (BPMR) system, which can obtain a better bit error rate (BER) performance. We focus on the three-track/threehead BPMR channel and propose the ITI subtraction technique that performs together with a rate-5/6 two dimensional (2D) modulation code. Since the coded system can provide the estimated recorded bit sequence with a high reliability rate for the center track. However, the upper and lower data sequences still be interfered with their sidetracks, which results to have a low reliability rate. Therefore, we propose to feedback the data from the center and upper tracks for subtracting the ITI effect of the lower track. Meanwhile, the feedback data from the center and lower tracks will be also used to subtract the ITI effect of the upper track. The use of our proposed technique can effectively reduce the severity of ITI effect which caused from the two sidetracks. The computer simulation results in the presence of position and size fluctuations show that the proposed system yields better BER performance than a conventional coded system, especially when an areal density (AD) is ultra high.

Warisarn, Chanon

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