Sokjabok, Siwakon

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Sokjabok, Siwakon
Alternative Name
Sokjabok, S.
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Email
siwakon.so@kmitl.ac.th

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    Item type:Publication,
    Symbol-flipping method for block decoding in bit-patterned magnetic recording
    (2021-05-19)
    Sokjabok, Siwakon
    ;
    Mattayakan, Mutita
    ;
    Warisarn, Chanon
    ;
    Koonkarnkhai, Santi
    ;
    Kovintavewat, Piya
    Bit-patterned magnetic recording (BPMR) technology can provide an areal density (AD) up to 15 Terabit per square inch (Tb/in2). However, the consequence of an increased AD results in severe inter-symbol interference (ISI) and inter-track interference (ITI). In practice, a run-length limited (RLL) code can be used to alleviate this problem. Therefore, this research proposes a symbol-flipping method in an iterative detection scheme between a soft-output Viterbi algorithm (SOVA) detector and an RLL decoder to help reduce errors resulting from these two interferences in a BPMR system. Simulation results reveal that the proposed system performs better than the same system architecture without the symbol-flipping method by 0.5 decibels at an AD of 5 Tb/in2.
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    Item type:Publication,
    Modified 2D Viterbi Algorithm using 2D Modulation Encoding Constraints in BPMR Systems
    (2020-06-01)
    Sokjabok, Siwakon
    ;
    Warisarn, Chanon
    ;
    Koonkarnkhai, Santi
    ;
    Lee, Jaejin
    The severity of inter-symbol interference (ISI) and inter-track interference (ITI) effects caused by the reduction of the spacing between bit islands in the along- and across-track directions to acquire ultra-high areal densities (ADs) is the main problem in bit-patterned magnetic recording (BPMR) systems. We call these two effects as two-dimensional (2D) interference, which can degrade the overall system performance. Practically, a one-dimensional (1D) modulation code, e.g., run-length limited (RLL) code, is essentially utilized to prevent the severe ISI effect. The use of 2D detectors is also one of the important ways to cope with the severe ITI; however, its complexity is quite high. To avoid the severe ITI effect and complex 2D detectors; therefore, we propose to apply the 1D RLL code as the 2D modulation code. Then, the 2D modulation encoding constraint is employed to reduce the number of states and branches in the trellis of the proposed modified 2D Viterbi detector. Simulation results reveal that the proposed detector not only delivers a lower complexity but also provides superior bit error rate gain, especially at ultra-high ADs and/or large location fluctuation.
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    Item type:Publication,
    An improvement of BER using two-dimensional constrained code for array-reader-based magnetic recording
    (2021-05-01)
    Sokjabok, Siwakon
    ;
    Koonkarnkhai, Santi
    ;
    Lee, Jaejin
    ;
    Warisarn, Chanon
    To achieve ultra-high areal densities in future magnetic recording technologies such as bit-patterned magnetic recording (BPMR) systems, each bit-island must be closely moved. However, the reduction of bit island spacing always leads to both inter-symbol interference (ISI) and inter-track interference (ITI), which can degenerate system performance. Previously, a one-dimensional (1D) run-length limited (RLL) code was employed to efficiently avoid the ISI effect, while a two-dimensional (2D) detector is widely utilized to deal with the ITI effect as well. However, its complexity is higher than the traditional 1D detector. Therefore, to avoid the fatal data patterns that lead to severe ITI effect, we first present the application of 1D RLL code to be as the 2D modulation code in the multi-head multi-track BPMR systems. Moreover, we also present the modified 2D Viterbi detector that is designed based on our proposed encoding condition. The numbers of state and branch in the traditional trellis's structure are properly reduced according to encoding condition, thus it does not only provide a lower complexity but also operate better than the traditional 2D Viterbi detector. Results reveal that our proposed coding scheme and modified 2D Viterbi detector can efficiently protect and cope with the ITI effect.