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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/in2 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.
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Three-Track Detection Using a Multilayer Perceptron for Dual-Layer Bit-Patterned Magnetic Recording Systems
(2026-01-01)
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 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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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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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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Mitigating Track Misregistration Using the DBSCAN Algorithm for Single-Reader/Two-Track Reading in Shingled Magnetic Recording Systems
(2026-01-01)
Kochcha, Pijit
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Kankhunthod, Kittipon
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Warisarn, Chanon
Shingled magnetic recording (SMR) systems can effectively reduce track width using the shingled writing technique, resulting in significantly higher areal density than conventional magnetic recording. However, track misregistration (TMR) still frequently occurs, leading to read errors and reduced signal processing performance. To address this, we propose a method for estimating TMR levels for single-reader/two-track reading in the SMR system using a density-based spatial clustering of applications with noise (DBSCAN) algorithm. Furthermore, we also present a mitigation method for TMR effects using the DBSCAN algorithm. In the TMR-level estimation process, the equalized signal from the first equalizer is fed into the first DBSCAN algorithm. The estimated TMR level is then used to select the appropriate equalizer to equalize the readback signal. Finally, the DBSCAN-based detector is used to detect the equalized signal. Simulation results at an areal density of 2 Tb/in2 demonstrate that our proposed method can accurately predict TMR levels, effectively mitigate TMR effects, and improve overall recording performance in terms of bit-error rate.
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Enhancing Signal Processing Capability with Tabu Search Algorithm Utilization for Rate-4/5 Modulation Coded Bit-Patterned Magnetic Recording
(2025-12-01)
Mattayakan, Mutita
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Warisarn, Chanon
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Lee, Jaejin
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Kankhunthod, Kittipon
To meet the growing demand for higher storage capacities, bit-patterned magnetic recording (BPMR) has emerged as a leading solution for achieving ultra-high user densities (UDs). However, BPMR systems are significantly impacted by two-dimensional (2D) interferences, specifically inter-symbol interference (ISI) and inter-track interference (ITI), which can degrade the quality of the readback signal. This paper introduces a rate-4/5 constructive ITI (CITI) modulation scheme, combined with a Tabu search (TS)-based error correction algorithm, to address the limitations of conventional CITI modulation codes. In the original encoding scheme, some codewords still contain forbidden patterns within their borders. The TS algorithm enhances the performance of the outermost tracks by refining unreliable bits identified through a distance-based reliability metric, which differs from earlier TS-based detectors that were directly used for multi-track detection. A proposed soft-information adjuster is then used to correct the poor reliability of soft information, resulting in improved soft-information reliability and decoding performance. A modified TS detector is also proposed, where the single-bit criterion for selecting the number of input bits is adopted, to improve neighbor selection and better align with the signal characteristics of the inner tracks. Simulation results show that the proposed system can achieve up to 2.7 dB and 4.0 dB improvements in bit error rate (BER) at a user density (UD) of 2.4 Terabits per square inch, compared to conventional uncoded and coded systems, respectively, while also reducing computational complexity. Furthermore, the results also imply that when the recording systems must operate under fluctuations in the size and position of the bit-island, our proposed system can provide superior performance.
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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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Double-Track PRML Detection for Two-Track Reading with a Wide-Track Reader in Shingled Magnetic Recording Systems
(2025-09-01)
Khametong, Anawin
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Greaves, Simon John
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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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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
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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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Study of CNN-Based Data Detection in Dual-Layer Bit-Patterned Magnetic Recording Systems
(2025-01-01)
Sangthong, Siraphop
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Sokjabok, Siwakon
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Khametong, Anawin
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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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