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/in2, 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/in2.
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Symbol-flipping method for block decoding in bit-patterned magnetic recording
(2021-05-19)
Sokjabok, Siwakon
;
Mattayakan, Mutita
;
Warisarn, Chanon
;
Koonkarnkhai, Santi
;
Kovintavewat, Piya
Bit-patterned magnetic recording (BPMR) technology can provide an areal density (AD) up to 15 Terabit per square inch (Tb/in2). However, the consequence of an increased AD results in severe inter-symbol interference (ISI) and inter-track interference (ITI). In practice, a run-length limited (RLL) code can be used to alleviate this problem. Therefore, this research proposes a symbol-flipping method in an iterative detection scheme between a soft-output Viterbi algorithm (SOVA) detector and an RLL decoder to help reduce errors resulting from these two interferences in a BPMR system. Simulation results reveal that the proposed system performs better than the same system architecture without the symbol-flipping method by 0.5 decibels at an AD of 5 Tb/in2.
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Enhancing Log-Likelihood Ratios with Mutual Information on Three-Reader One-Track Detection in Staggered BPMR Systems
(2025-03-01)
Rueangnetr, Natthakan
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Koonkarnkhai, Santi
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Kovintavewat, Piya
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Greaves, Simon John
;
Warisarn, Chanon
Because so much information is currently being shared online, there has been a sharp rise in the need for data storage devices over the past ten years. The main storage option is the hard disk drive (HDD), which is less expensive than some other types of data storage. Physical constraints, such as the superparamagnetic limit, are difficult to overcome using existing HDD technology. Consequently, bit-patterned magnetic recording (BPMR) has emerged as a potential solution, offering higher areal densities whilst maintaining thermal stability. Nevertheless, BPMR poses new challenges, such as inter-symbol interference and inter-track interference. Consequently, a number of approaches, such as staggered island layouts and array-reader magnetic recording, have been proposed to overcome these issues. However, this article proposes a three-reader one-track detection method to enhance data retrieval in a staggered BPMR system. Leveraging three-track reading for one-track detection, we obtain three readback signals that function as mutual data sequences. This substantially enhances the detection process in one-dimensional partial-response maximum-likelihood channels. Next, using these mutual data sequences, four novel techniques are presented to enhance bit-error rate (BER) performance and detection accuracy: hard-information flipping, maximum soft-information finding, bit-summation detection, and multilayer perceptron (MLP). This study shows that these proposed techniques can provide better BER performance compared with conventional methods and that the MLP is the most effective technique in enhancing system performance.
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Mitigation of TMR Using Energy Ratio and Bit-Flipping Techniques in Multitrack Multihead BPMR Systems
(2017-11-01)
Warisarn, Chanon
;
Busyatras, Wiparat
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Myint, Lin M.M.
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Koonkarnkhai, Santi
;
Kovintavewat, Piya
Track misregistration (TMR) in ultra-high density bit-patterned media recording (BPMR) is one of the crucial problems, because it can severely degrade the overall system performance. In practical, TMR can be detected and adjusted by a servo control loop system. However, this paper proposes to utilize multiple readback signals obtained from the optimized positioning of the two side read head closer to the main read head to improve the TMR prediction process in a multitrack multi-head BPMR system with position jitter noise. In addition, we also propose the soft-information exchange and the bit-flipping techniques for the multitrack data detection, so as to improve the bit-error rate (BER) performance of all three data tracks simultaneously. Simulation results indicate that the proposed system is superior to the conventional system, especially, when the amount of TMR and position jitter is high. Furthermore, we also found that the upper and lower read heads, which are moved closer to the center track by 25% of a track pitch, will provide the best BER performance with and without position jitter noise.
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Three-Track Detection Using a Multi-Layer Perceptron for Dual-Layer Bit-Patterned Magnetic Recording Systems
(2025-01-01)
Koonkarnkhai, Santi
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Plotchu, Siriphon
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Martnok, Warunee
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Rueangnetr, Natthakan
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Kilaso, Sathapath
This paper proposes a multi-layer perceptron (MLP)-based three-track detection method for dual-layer bit-patterned magnetic recording systems. Three architectures are explored: one MLP for three tracks, two MLPs for upper and lower layers, and three individual MLPs per track. Simulation results show that all MLP-based methods outperform conventional partial response maximum likelihood detection, especially under high areal density and complex interference. Among them, the two-MLP system achieves the best bit-error rate performance by effectively separating detection tasks across layers.
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Inter-Layer Interference (ILI) Suppression in Dual-Layer Bit-Patterned Magnetic Recording Systems
(2025-01-01)
Rueangnetr, Natthakan
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Koonkarnkhai, Santi
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Greaves, Simon John
;
Warisarn, Chanon
Dual-layer bit-patterned magnetic recording (DL-BPMR) systems are promising for achieving higher areal densities. However, they face significant challenges, including inter-symbol interference (ISI), inter-track interference (ITI), and inter-layer interference (ILI). To address these issues, this work proposes integrating a sum-soft-information (SSI) technique and an ITI suppression method to enhance detection reliability. The SSI technique is initially used to improve the reliability of the log-likelihood ratio for the bottom layer signal by leveraging the mutual information derived from a staggered array reader configuration. The enhanced data sequence from the bottom layer is subsequently utilized to suppress ILI by applying a weighting before it is subtracted from the top layer readback signals. Simulation results demonstrate that the proposed method significantly improves bit error rate (BER) performance compared to conventional single-layer and dual-layer BPMR systems, particularly at a user density of 4.0 Tb/in2, making it a promising approach for next-generation high-density magnetic recording.
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Soft Information Adjustor for Four-Head/Two-Track (4H/2T) Bit-Patterned Magnetic Recording
(2022-01-01)
Rueangnetr, Natthakan
;
Warisarn, Chanon
;
Koonkarnkhai, Santi
;
Kovintavewat, Piya
To mitigate the two-dimensional (2D) interference and track misregistration (TMR) effect, we have previously proposed a TMR correction method combined with the soft-information adjustor (SIA) technique. In practice, the SIA technique uses the advantage of a 2D soft-output Viterbi algorithm (SOVA) detector to improve the reliability of the log-likelihood ratio (LLR) before deciding the estimated user bits. To further improve its performance, this paper proposes a novel SIA scheme by exploiting the advantage of the 2D SOYA detector to improve the LLR reliability of the estimated data bits for the considered upper- and lower-track in four-head/two-track (4H/2T) bit-patterned magnetic recording system. The simulation results indicate that the proposed system can deliver a better BER performance over the conventional SIA system, in particular when the system experiences media noise.
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An Intertrack Interference (ITI) subtraction scheme for bit-patterned media recording
(2021-05-19)
Buajong, Chaiwat
;
Warisarn, Chanon
;
Koonkarnkhai, Santi
;
Kovintavewat, Piya
Currently, hard disk drive has been struggled to overcome the super-paramagnetic limit that restricts the density increment. Bit-patterned magnetic recording (BPMR) is a candidate that can increase an areal density (AD) up to 4 Tb/in2. However, inter-track interference (ITI) arising from a narrow track width at high AD severely degrades the system performance. This study proposes the ITI subtraction technique with turbo iteration in a coded BPMR system. This method refines the equalized sequence by subtracting the ITI using an imitated ITI sequence that is generated by the soft information obtained from turbo iteration and ITI coefficients. The refined sequence that contains the partial ITI is sent to the turbo iteration as many rounds as needed. Simulation results indicate that the proposed system outperforms the conventional system whether or not media noise is considered.
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Three-Track Detection Using a Multilayer Perceptron for Dual-Layer Bit-Patterned Magnetic Recording Systems
(2026-01-01)
Koonkarnkhai, Santi
;
Plotchu, Siriphon
;
Martnok, Warunee
;
Rueangnetr, Natthakan
;
Kilaso, Sathapath
This article proposes a multilayer perceptron (MLP)-based three-track detection method for dual-layer bit-patterned magnetic recording (BPMR) systems. Three different MLP architectures are explored and evaluated, namely: 1) a single MLP detecting all three tracks simultaneously; 2) three MLPs, each detecting one track independently; and 3) two MLPs dedicated to upper and lower recording layers. Simulation results show that the proposed MLP-based systems outperform the conventional partial-response maximum-likelihood (PRML) detection scheme, particularly under severe interferences and high areal density (AD). Among the proposed systems, the two-MLP architecture offers the optimal balance between detection accuracy and computational complexity, making it the most promising solution for future high-density magnetic recording systems.
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A Novel ITI Suppression Technique for Coded Dual-Track Dual-Head Bit-Patterned Magnetic Recording Systems
(2020-01-01)
Koonkarnkhai, Santi
;
Warisarn, Chanon
;
Kovintavewat, Piya
Generally, an intertrack interference (ITI) is a critical problem in bit-patterned magnetic recording (BPMR) systems that can attain an areal density (AD) up to 4 Tb/in2. Unavoidably, at high ADs, a very narrow track width must be employed, leading to severe ITI and unacceptable system performance. To tackle the ITI; therefore, this article introduces a novel ITI suppression technique for coded dual-track dual-head (DTDH) BPMR systems. At the first turbo iteration, the weighted readback signal of the adjacent track served as an estimated ITI signal is utilized for subtracting from the target readback signal to subside the ITI effect, before passing the refined readback signal to a turbo equalizer. Nonetheless, for the second turbo iteration onwards, the estimated ITI signal generated by the soft information obtained from a decoder at each turbo iteration will be then employed to subtract from the target readback signal during the turbo decoding process. Computer simulation results demonstrate that the proposed system can provide better performance than the DTDH system using a hard ITI suppression technique as well as the conventional system using one read head to decode one data track for all ADs, because the proposed technique can estimate the ITI signal well. Furthermore, when considering the recording system under the effects of media noise and track mis-registration, we also found that the proposed system is more robust than other systems.

Warisarn, Chanon

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