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Subject: search.filters.subject.2D modulation code

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    Soft-Decision Algorithm of a Rate-5/6 2D Modulation Code for SHTR in Staggered BPMR Systems
    (2022-01-01)
    Kanjanakunchorn, Chavisa
    ;
    Warisarn, Chanon
    With an increasing demand for recording data storage, this paper is interested in magnetic recording in bit-patterned media recording (BPMR) systems. The main problem of BPMR system from track width and bit length decreasing is two-dimensional (2-D) interference, consisting of inter-symbol interference and inter-track interference. One thing that solved this problem is 2-D modulation code of a rate-5/6 for single-head/two-track reading with staggered bit islands. Moreover, we also improve the performance of system by soft decision algorithm and low-density parity-check code because it can do an iterative process. The soft information is created by log-likelihood ratio by using a look-up table of a rate-5/6 through the Boolean logic circuit equation. After that, this soft information is brought to modified one-dimensional (1-D) soft-output Viterbi algorithm detector. At the same code rate of 5/6 and with bit error rate of 10-4, the simulation results show that our proposed scheme at an areal density of 3 Terabit per square inch, is better than system that performs without 2-D modulation code for 2 dB. Moreover, it is also better than previously proposed system that uses hard decisions with 2-D modulation code for 4 dB.
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    A simple 2D modulation code in single-reader two-track reading BPMR systems
    (2021-02-01)
    Busyatras, Wiparat
    ;
    Warisarn, Chanon
    ;
    Koonkarnkhai, Santi
    ;
    Kovintavewat, Piya
    A reduction in the track width of magnetic recording systems results in a welcome increase in Areal Density (AD), but can severely deteriorate system performance in the unfortunate appearance of extreme Inter-Track Interference (ITI). The effect of severe ITI may be mitigated by using coding schemes. In this paper, therefore, we present a rate-5/6 2-Dimensional (2D) modulation code based on a proposed Single-Reader/Two-track Reading (SRTR) technique to cope with this serious problem in staggered Bit-Patterned Magnetic Recording (BPMR) systems. We then evaluate the Bit-Error Rate (BER) performance of the proposed system in the presence of media noises, e.g., position and size fluctuations. Our simulation results indicate that, at the same User Density (UD), the proposed system performs better than an uncoded system by about 1.0 ​dB ​at the BER of 10<sup>−5</sup> and is also superior to the conventional recording system.
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    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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    An effective track width with a 2d modulation code in Two-Dimensional Magnetic Recording (TDMR) systems
    (2019-01-01)
    Pituso, Kotchakorn
    ;
    Warisarn, Chanon
    ;
    Tongsomporn, Damrongsak
    When the track density of two-dimensional magnetic recording (TDMR) systems is increased, intertrack interference (ITI) inevitably grows, resulting in the extreme degradation of an overall system performance. In this work, we present coding, writing, and reading techniques which allow TDMR systems with multi-readers to overcome severe ITI. A rate-5/6 two-dimensional (2D) modulation code is adopted to protect middle-track data from ITI based on cross-track data dependence. Since the rate-5/6 2D modulation code greatly improves the reliability of the middle-track, there is a bit-error rate gap between middle-track and sidetracks. Therefore, we propose the different track width writing technique to optimize the reliability of all three data tracks. In addition, we also evaluate the TDMR system performance using an user areal density capability (UADC) as a main key parameter. Here, an areal density capability (ADC) can be measured by finding the bit-error rate of the system with sweeping track and linear densities. The UADC is then obtained by removing redundancy from the ADC. Simulation results show that a system with our proposed techniques gains the UADC of about 4.66% over the conventional TDMR systems.
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    A simple inter-track interference subtraction technique in Bit-Patterned Media Recording (BPMR) systems
    (2018-05-01)
    Buajong, Chaiwat
    ;
    Warisarn, Chanon
    In this paper, we demonstrate how to subtract the intertrack interference (ITI) before the decoding process in multi-track multihead bit-patterned media recording (BPMR) system, which can obtain a better bit error rate (BER) performance. We focus on the three-track/threehead BPMR channel and propose the ITI subtraction technique that performs together with a rate-5/6 two dimensional (2D) modulation code. Since the coded system can provide the estimated recorded bit sequence with a high reliability rate for the center track. However, the upper and lower data sequences still be interfered with their sidetracks, which results to have a low reliability rate. Therefore, we propose to feedback the data from the center and upper tracks for subtracting the ITI effect of the lower track. Meanwhile, the feedback data from the center and lower tracks will be also used to subtract the ITI effect of the upper track. The use of our proposed technique can effectively reduce the severity of ITI effect which caused from the two sidetracks. The computer simulation results in the presence of position and size fluctuations show that the proposed system yields better BER performance than a conventional coded system, especially when an areal density (AD) is ultra high.