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Author: search.filters.author.Buajong, ChaiwatSubject: search.filters.subject.intertrack interference

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    Optimal Array-Reader and Track Misregistration Mitigation Method in a Three-Reader/Four-Track Reading Bit-Patterned Magnetic Recording System
    (2020-01-01)
    Kankhunthod, Kittipon
    ;
    Buajong, Chaiwat
    ;
    Warisarn, Chanon
    Track misregistration (TMR) is one of several problems in ultrahigh areal density bit-patterned magnetic recording (BPMR) systems, in which the distances between bit-islands are very narrow in both cross-track and down-track directions.Unfortunately,distance reduction leads to intersymbol interference and intertrack interference (ITI) effects,which cause system performance degradation. To deal with these effects, we develop the optimal position of an array-reader based on a three-reader/four-track reading BPMR system that is combined with a simple two-dimensional rate-3/4 modulation code and ITI subtraction technique,which delivers the best avoidance of the ITI effect from sidetracks.We model TMR estimation and mitigation methods using readback signals that are obtained from the optimal array-readers to improve bit error rate (BER) performance.The variance-ratio of these readback signals is used to estimating the TMR levels,whereas a pair of the target’s and equalizer’s coefficients,accordingly designed to the estimated TMR levels,is adopted for mitigating the TMR effect. Simulation results show that our methods provide a high TMR estimation accuracy and gain a superior BER performance compared with the recording system without these techniques under the same user density.
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    Modified Multitrack Joint Two-Dimensional Viterbi Detectors for Rate-4/5 and Rate-5/6 Modulation Codes in Bit-Patterned Magnetic Recording Systems
    (2020-01-01)
    Buajong, Chaiwat
    ;
    Warisarn, Chanon
    For an ultrahigh areal-density bit-patterned magnetic recording, system performance is severely degraded by intertrack interference (ITI). Rate-4/5 and rate-5/6 modulation codes were introduced to avoid data patterns that can cause severe ITI. However, their decoders might not be able to correctly perform for data patterns that do not match with their look-up tables during the decoding process. To further improve system performance, we use a multitrack joint two-dimensional (2-D) Viterbi detector for the recommended systems. We also use a modified trellis structure with lower complexity when compared to a conventional joint 2-D detector, which is designed based on their encoding conditions. Simulation results show that our systems outperform the conventional system, especially when they are investigated in a media-noise environment.
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    Improvement in Bit Error Rate with a Combination of a Rate-3/4 Modulation Code and Intertrack Interference Subtraction for Array-Reader-Based Magnetic Recording
    (2019-01-01)
    Buajong, Chaiwat
    ;
    Warisarn, Chanon
    To improve the bit-error-rate (BER) performance of an ultrahigh-density bit-patterned magnetic recording (BPMR) system, the intersymbol interference and intertrack interference (ITI) effects resulting from the reduction of spacing between bit islands in both along-track and across-track directions must be efficiently handled. Array-reader-based BPMR is considered a key technology for future magnetic recording due to its advantages, such as its diversity gain against noise and ITI cancellation. This letter proposes a three-reader, four-track system where a simple rate-3/4 two-dimensional (2-D) modulation code and a new ITI subtraction technique are used to improve recording system performance. Moreover, a 2-D Viterbi detector is modified in accordance with the ITI subtraction scheme, which leads to lower complexity and better BER performance. Simulations demonstrate improvement in performance gains under position and size fluctuation effects.