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Subject: search.filters.subject.Inter-track interference

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    An Intertrack Interference (ITI) subtraction scheme for bit-patterned media recording
    (2021-05-19)
    Buajong, Chaiwat
    ;
    Warisarn, Chanon
    ;
    Koonkarnkhai, Santi
    ;
    Kovintavewat, Piya
    Currently, hard disk drive has been struggled to overcome the super-paramagnetic limit that restricts the density increment. Bit-patterned magnetic recording (BPMR) is a candidate that can increase an areal density (AD) up to 4 Tb/in2. However, inter-track interference (ITI) arising from a narrow track width at high AD severely degrades the system performance. This study proposes the ITI subtraction technique with turbo iteration in a coded BPMR system. This method refines the equalized sequence by subtracting the ITI using an imitated ITI sequence that is generated by the soft information obtained from turbo iteration and ITI coefficients. The refined sequence that contains the partial ITI is sent to the turbo iteration as many rounds as needed. Simulation results indicate that the proposed system outperforms the conventional system whether or not media noise is considered.
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    A simple 2/3 modulation code and bit-flipping technique in bit-patterned media recording systems
    (2018-07-02)
    Busyatras, Wiparat
    ;
    Poompuang, Pitaya
    ;
    Myint, Lin M.M.
    ;
    Warisam, Chanon
    Two-dimensional (2-D) modulation code is considered as one of the key schemes to improve the areal density capability for next generation magnetic recording e.g., bit-patterned media recording (BPMR) technology, due to its advantages such as severe inter-track interference (ITI) suppression and user densities escalation. In this work, a rate-2/3 2-D modulation with a three-reader three-track (3R3T) system is studied where the positions of reader are accordingly optimized with the encoded criteria to obtain the highest bit-error rate (BER) performance. Moreover, we also propose a bit-flipping technique which is one way to extremely improve the overall system performance. Here, the soft-information that are obtained from soft-output Viterbit algorithm (SOVA) detectors will be improved according with the encoded criteria before sending to the proposed decoder. Simulation results demonstrate that significant performance gain can be achieved using these two proposed approaches.
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    Single-track equalization method with TMR correction system based on cross correlation functions for a patterned media recording system
    (2017-01-01)
    Myint, Lin Min Min
    ;
    Warisarn, Chanon
    ;
    Busyatras, Wiparat
    ;
    Kovintavewat, Piya
    Bit-patterned media recording (BPMR) is a promising technology for ultra-high density media, however, there are some challenges that need to be addressed including two-dimensional (2D) interference, and track mis-registration (TMR). The system can experience TMR due to misalignment of the head and the track center. Conventionally, TMR is tackled using a servo system in which the head position offset is estimated by processing the overhead servo sequences before reading the data sequences. However, TMR impairment can also occur when the head is reading data sequences that are beyond the servo mechanism. To address this problem, we proposed TMR detection and correction techniques based on our previous work involving a single-track equalization method for a BPMR system using cross-correlation functions between the single readback signal and each of the training sequences from three adjacent tracks. In this proposed technique, the presence and level of TMR is detected and estimated based on the changes in the value of mean square error (MSE) between the equalized and feedback signals from the detectors after passing through a one-dimensional (1D) target for each sequence. Then, the estimated TMR levels are used in selecting the appropriate equalizer and the generalized partial response (GPR) target pair to tackle the TMR from the readback signal. The simulation results show improvement in the data recovery of a BPMR system using the proposed method when the system is experiencing 2D interference and TMR impairment.
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    Performance of Log-MAP algorithm for graph-based detections on the 2-D interference channel
    (2014-01-01)
    Sopon, Thanomsak
    ;
    Supnithi, Pornchai
    ;
    Vichienchom, Kasin
    The read channel of magnetic recording system is affected by two-dimensional interference channel that is a combination of inter-symbol interference and inter-track interference. Inter-track interference is one of the biggest challenges in the high density magnetic recording systems and it can degrade the performance of the channels. In this work, we compare three variations of log-MAP algorithms for graph-based detectors in two-dimensional interference channels. The simulation results show the performance of the graph-based detector with the full log-MAP and extended log-MAP algorithms achieve the gains of about 0.1 and 0.05 dB at BER = 10<sup>-5</sup>, over the max approximation on bit patterned media recording system with the areal density 2.5 Tbits/in<sup>2</sup>. © 2014 IEEE.
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    Iterated Viterbi detection methods for a 2-D bit patterned mediastorage
    (2010-01-01)
    Myint, Lin M.M.
    ;
    Supnithi, Pornchai
    ;
    Tantaswadi, Prinya
    In this paper, we studied the performance of the iterated Viterbi detection methods using the multi-track multi-head processing for a bit patterned media (BPM) channel with a two-dimensional interference consisting of inter-symbol interference (ISI) and inter-track interference (ITI). In each method, three Viterbi detectors are employed to process the three readback signals. In their trellises, the number of states is designed based on the ISI only. After the first iteration, the estimated output sequences are exchanged between the adjacent detectors as the ITI estimations and then used in the metric calculation of next iteration. When compared with other methods, the simulation results show that the proposed methods achieve significant gains. We also investigated the performance of the proposed methods for the BPM channel with different media noise levels. Finally, the computational complexity of all detectors is compared.