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 57

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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
;
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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Reliability Test Techniques in Tabu Search Detection for Enhancing BER Performance of Array Reader Bit-Patterned Magnetic Recording Systems
(2026-01-01)
Mattayakan, Mutita
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Rueangnetr, Natthakan
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Kankhunthod, Kittipon
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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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Codeword design of a Rate-5/6 for single-reader two-track reading in BPMR systems
(2021-05-19)
Mattayakan, Mutita
;
Sokjabok, Siwakon
;
Warisarn, Chanon
At present, the information storage demand of hard disk drive (HDD) was dramatically increasing every year. However, an increase of an areal density (AD) for bit-patterned media recording (BPMR) seems to be crucial for HDD industry. One of the main problems of BPMR system is two-dimensional interference effect that composes of inter-track interference (ITI) and inter-symbol interference (ISI), which still be the main challenge that we have to flounder to continuously enhance the efficiency of magnetic recording system. Therefore, this paper proposes a rate-5/6 2D modulation code to evolve bit error rate (BER) efficiency of a staggered single-reader two-track reading (SRTR) based BPMR systems. We select all 32 codewords from all 64 considered patterns according to the statistics principle considering. The first 32 patterns that provide the least error-bit number will then be defined as our proposed codewords. These selected patterns can efficiently avoid the forbidden patterns that means it is going to radically suppress both ISI and ITI effects. We simply encode by using a look-up table, while we use the Euclidean distance concept to recover user bits in the decoding process. From the simulation, we found that the proposed method shows a better BER efficiency than both the uncoded and conventional recording systems. Even we add more media noises, this proposed system still provides us with a better performance. Moreover, SRTR scheme offers us more satisfactory capability than the conventional recording systems.
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Double-Track PRML Detection for Two-Track Reading with a Wide-Track Reader in Shingled Magnetic Recording Systems
(2025-09-01)
Khametong, Anawin
;
Greaves, Simon John
;
Warisarn, Chanon
The utilization of two-track simultaneous reading is proposed to avoid the requirement for a narrow track reader in shingled magnetic recording systems, where partial response maximum likelihood detection and recursive decoding by oversampling techniques are employed for decoding. To develop effective decoding techniques when reading two tracks with a wide-track reader, we propose utilizing a pre-coding scheme along with a modified Viterbi detector. A pre-coder and an oversampling scheme are first adopted, where the sampling points are located at the centers of the front and rear halves of the recorded bits. The Trellis diagram of the conventional Viterbi algorithm is then modified according to all possible transitions of the readback signal obtained from two-track simultaneous reading. The proposed technique can simultaneously detect two data tracks. Simulation results indicate that at an areal density of 2 Tb/in<sup>2</sup>, the proposed system offers improved performance regarding the bit-error rate.
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Track Misregistration Estimation Technique Based on Hybrid K-Means and EM Algorithm in Bit-Patterned Media Recording Systems
(2025-01-01)
Kochcha, Pijit
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Kankhunthod, Kittipon
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Warisarn, Chanon
Track misregistration (TMR) in ultrahigh density bit-patterned media recording (BPMR) is a significant issue, severely degrading system performance. Although TMR can be managed by a servo control loop, this article proposes a hybrid TMR mitigation method based on K-means and expectation-maximization (EM) algorithms to enhance TMR prediction accuracy and improve bit-error-rate (BER) in multihead/multitrack BPMR systems. This method utilizes 2-D equalizer and 1-D generalized partial response (GPR) target coefficients for the soft-output Viterbi algorithm (SOVA) detector according to the estimated TMR level to mitigate this effect. Simulation results demonstrate that the proposed system significantly outperforms conventional systems, especially under high TMR conditions. The hybrid approach achieves high TMR estimation accuracy and delivers BER performance close to an ideal system with perfect TMR estimation, showing up to a 1.25 dB improvement in BER over systems without TMR mitigation. These findings underscore the effectiveness of the hybrid K-means-EM-based TMR estimator in enhancing system performance under various conditions.
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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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Track Mis-registration Correction Method in Two-Head Two-Track BPMR Systems
(2020-06-01)
Kankhunthod, Kittipon
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Busyatras, Wiparat
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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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Study of CNN-Based Data Detection in Dual-Layer Bit-Patterned Magnetic Recording Systems
(2025-01-01)
Sangthong, Siraphop
;
Sokjabok, Siwakon
;
Khametong, Anawin
;
Warisarn, Chanon
This paper introduces an innovative data detection system that utilizes convolutional neural networks (CNNs) for dual-layered bit-patterned magnetic systems. Using a mutual-information CNN architecture, the proposed system tackles the challenge of decoding overlapping readback signals from upper and lower layers. The sliding window detection schemes are implemented with input lengths of 6 (2×3) and 14 (2×7) bits, processing oversampled readback signals from a dataset of 1,000,000 bits. Simulation results conducted over a signal-to-noise ratio range of 10 to 24 dBs indicate that the CNN model with a larger input window significantly outperforms smaller input models and conventional partial response maximum likelihood detectors in terms of bit error rate. These findings illustrate the effectiveness of CNN-based detection in enhancing classification accuracy under high-noise conditions, paving the way for future ultra-high-density magnetic recording systems.
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Deep Neural Network Detection With an ITI Subtraction for Non-Uniform Track-Width Two-Dimensional Magnetic Recording
(2024-04-01)
Buajong, Chaiwat
;
Lee, Jaejin
;
Warisarn, Chanon
Continuously expanding the magnetic recording density results in unavoidable interferences including intersymbol interference (ISI) and intertrack interference (ITI) that both critically degrade the system performance. Even with advanced signal processing tools, two-dimensional magnetic recording (TDMR) still struggles to provide satisfactory performance. Thus, this article proposes the deep neural network (DNN)-based detection deployed in conjunction with an equalizer for the TDMR system. The coding scheme uses a low-density parity-check (LDPC) code, enabling the information exchange or the turbo decoding. The retrieval of data occurs within a group of three adjacent tracks. We also explore two different track configurations: uniform and non-uniform tracks that involve doubling the width of the middle track among the three adjacent tracks. The utilization of the highly reliable signal obtained from the double-width track enables the application of ITI subtraction technique, enhancing the information exchange. This technique can mitigate the ITI effect by subtracting the target signal with the imitated ITI signal. In addition, we investigate two different DNN architectures including the multilayer perceptron (MLP) and convolutional neural network (CNN), along with two scenarios for the detections in different passes of turbo decoding. The simulation results conducted on the Voronoi media model, with realistic grains and non-magnetic grain boundaries, show that the proposed detection systems with the non-uniform track configuration offer a performance gain up to 5.3 dB over the system with the uniform track configuration. Moreover, iteration for the turbo decoding passes incrementally improves the system performance in the proposed systems with the non-uniform track while the systems with the uniform track no longer provide performance gain as the number of iterations goes on.

Warisarn, Chanon

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