Rueangnetr, Natthakan

Preferred name

Alternative Name

Rueangnetr, N.

Main Affiliation

Integrated Innovative Technology

natthakan.ru@kmitl.ac.th

Now showing 1 - 10 of 19

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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
;
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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Combining Unequal Bit Islands and Coding Design for Areal Density Enhancing in Dual-Layer Bit-Patterned Magnetic Recording Systems
(2026-01-01)
Sriyapai, R.
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Rueangnetr, N.
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Koonkarnkhai, S.
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Warisarn, C.
In this work, we propose an alternating media structure for a dual-layer bit-patterned magnetic recording (DL-BPMR), in which the diameters of the bit islands in the bottom and top layers differ, with the bottom diameter 4 times that of the top. We then propose an encoding scheme that uses the larger bit island in the bottom layer for a parity bit to detect errors during decoding. Moreover, we suggest the log-likelihood ratio (LLR) flipping technique to improve decoding capability, which operates jointly during decoding. Simulation results show that at the same user density (UD), our proposed systems outperform the conventional single-layer (SL) BPMR. For instance, at a bit-error rate of 10<sup>-3</sup> and total UDs of 2.0 or 3.2 Terabit per square inch, the proposed systems provide approximately 0.8 dB and 1.2 dB, respectively, over the conventional SL-BPMR systems.
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Inter-Layer Interference (ILI) Suppression in Dual-Layer Bit-Patterned Magnetic Recording Systems
(2026-01-01)
Rueangnetr, Natthakan
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Koonkarnkhai, Santi
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Greaves, Simon John
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Warisarn, Chanon
Dual-layer bit-patterned magnetic recording (DL-BPMR) systems are promising for achieving higher areal densities (ADs). 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 ILI suppression method to enhance detection reliability. The SSI technique is initially used to improve the reliability of the log-likelihood ratio (LLR) for the bottom layer signal by leveraging the mutual information derived from a staggered array reader configuration. The enhanced data sequence of the bottom layer is subsequently utilized to suppress ILI by applying a weighting before being removed from the mixed readback signal. The separated readback signal of the top layer is then processed using well-predesigned equalizers and detectors. Simulation results demonstrate that the proposed method significantly improves bit error rate (BER) performance compared to conventional single-layer and DL-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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Feasibility Study of Implementing Simple Dual-bit Detection in Dual-Layer Bit-Patterned Magnetic Recording Systems
(2025-09-01)
Rueangnetr, Natthakan
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Greaves, Simon John
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Warisarn, Chanon
Dual-layer bit-patterned magnetic recording (DL-BPMR) systems, which combine bit-patterned magnetic recording (BPMR) and multi-layer magnetic recording technologies, are expected to increase the areal density (AD) of data storage up to 10 Terabits per square inch. However, to achieve this goal, several challenges must be overcome, including low response signals from the lower layer and interlayer interference. Therefore, this work proposes a signal processing technique to reduce the number of erroneous bits at the receiver. A simple dual-bit detection (SD-BD) method is proposed. Simulation results comparing the performance of a single-layer BPMR system with that of a DL-BPMR system using the SD-BD signal processing technique show that the latter can effectively reduce the bit error rate. The results indicate that the SD-BD technique has the potential to improve the read accuracy of the DL-BPMR system and is an essential step towards the future development of data recording technologies with higher AD.
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Optimization of Layer Thicknesses for Dual-Layer Bit-Patterned Media Recording (BPMR) Systems
(2024-01-01)
Rueangnetr, Natthakan
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Warisarn, Chanon
;
Greaves, Simon John
To increase the areal recording density of magnetic recording, we have investigated the effect of the thicknesses of the individual layers in dual-layer bit-patterned magnetic recording (BPMR) systems. The recording media consisted of two, discrete recording layers, separated by a non-magnetic spacer layer. The bottom recording layer thickness and head-medium spacing (HMS) were fixed, while the top recording layer thickness was varied to adjust the spacing between the reader and the bottom layer. By varying the layer thicknesses, the readback signal strengths from the top and bottom layers can be adjusted and balanced. To determine the bit-errorrate improvement needed to reach a target areal density of 4.0 Tbits/in2, i.e. 2.0 Tbits/in2 per layer, the readback signal was processed using an iterative method. The results showed that the proposed design could outperform a single-layer BPMR system.
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3/5 Decoder and LLR Estimator-based Multilayer Perceptron for SRTR Bit-Patterned Media Recording
(2022-01-01)
Rueangnetr, Natthakan
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Warisarn, Chanon
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Koonkamkhai, Santi
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Kovintavewat, Piya
To increase the data storage capacity of the hard disk drives for storing huge digital information that grows rapidly, one of the alternative technologies, bit-patterned media recording (BPMR), can support an areal density (AD) of up to 4 Terabits per square inch (Tb/in2). To increase AD; however, due to inter-track interference (ITI) and inter-symbol interference (ISI), which degrade system performance, when we must reduce the distance between bit-islands. In this work, we propose the rate-3/5 decoder and the log-likelihood ratio (LLR) estimator which performs together with the rate-3/5 constraint code based on the multilayer perceptron (MLP) under a single reader/two-track reading (SRTR) BPMR system. The results of our simulations show that, with the same 3 Tb/in2 user density (UD), when compared to both conventional uncoded and coded systems with and/or without media noise, the proposed system can achieve a lower signal to noise ratio (SNR) while maintaining the same bit error rate performance.
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Enhancing Signal Processing With Multilayer Perceptron Utilization for Bit-Patterned Magnetic Recording
(2025-01-01)
Rueangnetr, Natthakan
;
Greaves, Simon John
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Warisarn, Chanon
Bit-patterned magnetic recording aims to overcome the superparamagnetic limit and achieve higher areal density in magnetic recording, with improved thermal stability and reduced transition noise. However, the inter-symbol interference and inter-track interference effects remain crucial problems that must be addressed. This work introduces a multilayer perceptron-based equalizer operating in conjunction with an adaptive target scheme. Furthermore, we also propose using a multilayer perceptron-based detector to improve the overall recording performance. We evaluated our enhanced processing methods using regular and staggered bit-island arrangements. The simulation results indicate that the multilayer perceptron-based equalizer achieves lower mean square error values across all signal-to-noise ratio levels when compared to the conventional minimum mean square error equalizer. Additionally, the proposed multilayer perceptron-based detector performs slightly better than the multilayer perceptron-based equalizer. Also, these proposed techniques demonstrate superior bit error rate performance, even when considering bit-island position fluctuations.
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Double-layer magnetic recording with multilayer perceptron decoder for single-reader/two-track reading in BPMR systems
(2023-03-01)
Rueangnetr, N.
;
Koonkarnkhai, S.
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Kovintavewat, P.
;
Warisarn, C.
To expand an areal density of hard disk drives, bit-patterned magnetic recording (BPMR) using a patterned medium instead of a granular medium as employed in perpendicular magnetic recording is attracting much attention as the next-generation recording technology. To further increase the storage capacity of BPMR, multi-layer magnetic recording can be combined with BPMR. Therefore, this paper considers double-layer magnetic recording with a single-reader/two-track reading technique for the staggered BPMR system, which is performed together with a rate-3/5 modulation code. This paper proposes to utilize a multilayer perceptron decoder to decode and estimate the log-likelihood ratio value of the recorded bit sequence that is obtained from the equalized channel. Simulation results show that at a bit-error rate of 10-4, the proposed system with a double-layer recording medium can achieve an improvement gain of about 1.2 decibel if compared to that with a regular single-layer recording medium, even in the presence of media noise.
1
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Signal Processing Techniques for Enhancing an Areal Density in Two-Reader/Three-Track Detection of Staggered Bit-Patterned Magnetic Recording Systems
(2026-03-01)
Rueangnetr, Natthakan
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Wattanaphol, Satra Tor
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Kankhunthod, Kittipon
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Greaves, Simon J.
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Warisarn, Chanon
As the demand for digital storage capacity continues to grow, bit-patterned magnetic recording (BPMR) has emerged as a promising technology to overcome the superparamagnetic limit of conventional recording methods. Nevertheless, the extremely close spacing of magnetic islands in BPMR can result in significant signal corruption, particularly due to inter-track interference. This paper presents robust signal-processing schemes for a two-reader, three-track detection system in a staggered BPMR configuration to address these challenges. The first proposed method employs a sum-soft-information technique, which combines log-likelihood ratios from two detectors to maximize mutual information. This approach significantly improves the reliability of middle-track detection. We also propose the inter-track interference subtraction technique, in which the highly reliable data recovered from the middle track are used to reconstruct the interference signal, which is then subtracted from the upper and lower tracks using an optimized weighting factor. Simulation results at an areal density of 3.0 Tb/in<sup>2</sup> demonstrate that an optimized weighting factor of 1.78 effectively cancels interference. Moreover, the results indicate that our proposed scheme achieves a bit-error rate (BER) comparable to that of the three-reader, one-track detection BPMR systems. Furthermore, our method also demonstrates a lower BER for both adjacent tracks when compared to the conventional single-reader, two-track reading system, even in the presence of 10% media noise.
2
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Adaptive Designing Process of 2-D GPR Target and Equalizer based on BER in BPMR Systems
(2020-06-01)
Rueangnetr, Natthakan
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Warisarn, Chanon
;
Myint, Lin M.M.
In high areal density magnetic recording systems, two-dimensional (2-D) equalizer and 2-D generalized partial response (GPR) target are proposed to tackle the 2-D interference problem. However, the minimum mean squared error (MMSE) technique cannot provide the optimality of the 2D detector, particularly only partial side-track information are available in the designing process. Therefore, we develop an adaptive designing process to obtain the optimal equalizers and targets based on bit error rate (BER) for two-track two-head (2T2H) bit-pattern media recording (BPMR) read channel model. In the process, the coefficients of the 2-D equalizer and GPR target are computed using the MMSE technique first. Then these MMSE targets and equalizers are adaptively adjusted based on BER at the low SNR levels. In each iteration, the main side-track coefficients of the 2×3 GPR targets are adjusted based on the BER. The iterative process is continually operated until there will be enough low level of error. Finally, the performance of those equalizers and targets are evaluated under the 2T2H BPMR system.
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Rueangnetr, Natthakan

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