Rueangnetr, Natthakan

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Rueangnetr, Natthakan
Alternative Name
Rueangnetr, N.
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Email
natthakan.ru@kmitl.ac.th

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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
    ;
    Plotchu, Siriphon
    ;
    Martnok, Warunee
    ;
    Rueangnetr, Natthakan
    ;
    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
    ;
    Koonkarnkhai, Santi
    ;
    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/in<sup>2</sup>, 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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    Adaptive Designing Process of 2-D GPR Target and Equalizer based on BER in BPMR Systems
    (2020-06-01)
    Rueangnetr, Natthakan
    ;
    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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    Optimization of Layer Thicknesses for Dual-Layer Bit-Patterned Media Recording (BPMR) Systems
    (2024-01-01)
    Rueangnetr, Natthakan
    ;
    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
    ;
    Warisarn, Chanon
    ;
    Koonkamkhai, Santi
    ;
    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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    Deep Neural Networks based Soft-Information Improvement for Two-head/Two-Track Bit-Patterned Magnetic Recording
    (2022-01-01)
    Khametong, Anawin
    ;
    Rueangnetr, Natthakan
    ;
    Warisarn, Chanon
    ;
    Koonkarnkhai, Santi
    ;
    Kovintavewat, Piya
    To increase an areal density (AD) of an ultra-high density bit-patterned magnetic recording (BPMR) system, we have previously proposed a track misregistration (TMR) correction method combined with the soft information adjustor (SIA) to cope with the effects of TMR and two-dimensional (2D) interference. However, we found that soft information or log-likelihood ratio (LLR) can be improved to earn better bit-error-rate (BER) performances. In this work; therefore, we propose to use two types of deep neural networks (DNNs), i.e., multi-layer perceptron (MLP) and long short-Term memory (LSTM) network with identical parameter magnitude to improve overall system performance. Here, both DNNs are operated with an earlier SIA on a two-head/two-Track (2H2T) BPMR system. Numerical results show that our proposed methods can deliver better BER performance over the earlier SIA system at all TMR levels with and without position jitter noises at the AD of 3.0 Terabit per square inch.