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 59

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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
;
Koonkarnkhai, Santi
;
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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A two-dimensional coding design for staggered islands bit-patterned media recording
(2015-05-07)
Arrayangkool, A.
;
Warisarn, C.
This paper proposes a two dimensional (2D) staggered recorded-bit patterning (SRBP) coding scheme for staggered array bit-patterned media recording channel to alleviate the severe 2D interference, which requires no redundant bits at the expense of increased an additional memories. Specifically, a data sequence is first split into three tracks. Then, each data track is circularly shifted to find the best data pattern based on a look-up table before recording such that the shifted data tracks cause the lowest 2D interference in the readback signal. Simulation results indicate that the system with our proposed SRBP scheme outperforms that without any 2D coding, especially when an areal density (AD) is high and/or the position jitter is large. Specifically, for the system without position jitter at bit-error rate of 10-4, the proposed scheme can provide about 1.8 and 2.3 dB gains at the AD of 2.5 and 3.0 Tb/in.2, respectively.
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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
;
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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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/in2, the proposed system offers improved performance regarding the bit-error rate.
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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
;
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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Mitigating the Effects of Track Mis-Registration in Single-Reader/Two-Track Reading BPMR Systems
(2019-07-01)
Warisarn, Chanon
Bit-recording technologies that can provide areal densities (ADs) [patterned magnetic recording (BPMR) is expected to be one of the new magnetic ADs] of 1 Tera-bit per square inch or higher. To achieve these ADs, the space between tracks must be reduced, bringing them closer and closer together, leading to significant inter-track interference (ITI). Track mis-registration (TMR) or head offset can further degrade overall system performance. To mitigate the effects of ITI and TMR, we propose using a single-reader/two-track reading (SRTR) scheme together with an over-sampling technique on a staggered BPMR system. We also propose a TMR estimation technique based on a readback signal. Here, the readback signal is separated into two sequences, one odd and one even. Then, the energy ratio is calculated using these data sequences. The obtained relationship between the energy ratio and head offset can be utilized to predict the actual head offset occurrence in the reading process. Finally, a pairing of a monic constraint target and an equalizer that accordingly matches each estimated head offset level is adopted to deal with the TMR effect. The SRTR system can provide better bit-error-rate (BER) performance. Moreover, when TMR effects appear in the reading process, our proposed SRTR system with a TMR mitigation technique can yield better BER performance, especially at high head offset levels.
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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
;
Kankhunthod, Kittipon
;
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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An iterative TMR mitigation method based on readback signal for bit-patterned media recording
(2015-11-01)
Busyatras, Wiparat
;
Warisarn, Chanon
;
Myint, Lin M.M.
;
Supnithi, Pornchai
;
Kovintavewat, Piya
Off-track condition or track misregistration (TMR) is one of the most significant problems in the extremely high-density bit-patterned media recording (BPMR) system, since a track pitch becomes narrower. Typically, the TMR can be detected and handled by a servo system; however, it requires some special data to be inserted in the tracks so as to estimate the amount of head offset. Nonetheless, this paper proposes an iterative TMR mitigation method for BPMR systems based on the readback signals. First, we design several pairs of the 2-D asymmetric target and its corresponding 2-D equalizer that match the BPMR channel for each TMR level. Then, we exploit the three adjacent data tracks obtained from the low-density parity-check decoders to estimate the TMR level. Last, a pair of the 2-D asymmetric target and its corresponding 2-D equalizer that is best fit to the estimated TMR level will be used to alleviate the TMR effect in the readback signal for the next global iteration. Simulation results indicate that the proposed system can effectively estimate the TMR level and performs better than the conventional system without a TMR mitigation method, especially when the TMR level is high and/or the position jitter is large.
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An Intertrack Interference Subtraction Scheme for a Rate-4/5 Modulation Code for Two-Dimensional Magnetic Recording
(2016-01-01)
Pituso, Kotchakorn
;
Warisarn, Chanon
;
Tongsomporn, Damrongsak
;
Kovintavewat, Piya
The performance of a rate-4/5 modulation code is evaluated in two-dimensional magnetic recording (TDMR) channels, where a magnetic medium is described by a discrete Voronoi model, and the two-dimensional sensitivity function of the reader is adopted to generate the TDMR readback signal. Since the read-head sensitivity function covers many tracks, it causes intertrack interference (ITI) that can deteriorate the system performance. Therefore, this letter proposes an ITI subtraction scheme in conjunction with the rate-4/5 modulation code in a coded TDMR channel to mitigate the ITI effect embedded in the readback signals before performing an iterative decoding process. We also investigate the data-dependent readback amplitude distributions and evaluate the TDMR system performance via computer simulation. Results show that the proposed scheme helps improve the TDMR system performance, especially when the areal density is high.
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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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