Warisarn, Chanon
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Preferred name
Warisarn, Chanon
Alternative Name
Warisarn, C.
Main Affiliation
Email
chanon.wa@kmitl.ac.th
46 results
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Item type:Publication, A Soft ITI Mitigation Method for Coded 2H2T BPMR Systems(2019-06-01); - Some of the metrics are blocked by yourconsent settings
Item type:Publication, A bit-flipping technique based on 2D modulation constraint in BPMR systems(2018-10-24); Inter-track interference (ITI) cancelation is one of the considerable challenges for high areal density (AD) magnetic recording such as in bit-patterned media recording (BPMR) systems. In literature, the two-dimensional (2D) modulation codes have been proposed to cancel the ITI effect [1, 2] which can efficiently improve the overall system performance, e.g., a rate-5/6 2D modulation code [2]. Although the rate-5/6 modulation code ensures that the readback signal of the center track will not be corrupted by severe ITI; however, both the upper and lower tracks can still be interfered by their sidetracks. To improve this shortcoming; therefore, we propose the bit-flipping technique that performs together with the rate-5/6 2D modulation code. Here, the relationship between the data encoding condition and soft-information obtained from the soft output Viterbi algorithm (SOVA) detector is utilized to be a criterion for flipping the ambiguous data bits. Simulation results indicate that the proposed system is better than the conventional coded system under with/without media noise and track mis-registration. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Unbalanced track pitch combined with 2D modulation code in TDMR systems(2018-10-24); Tongsomporn, D.Two-dimensional magnetic recording (TDMR) [1, 2] is a promising high density storage technology, which is expected to increase an areal density (AD) up to 10 terabit per square inch (Tbpsi). This technology is required write narrow-read wide technique that opposite to write wide-read narrow of one-dimensional (1D) read channel. The narrow track writing operated by shingled writing can greatly improve track per inch (TPI) gain. However, the side reading effect of reader is an unwanted situation because the intertrack interference (ITI) from sidetracks, which degrades the overall system bit error rate (BER) performance. Therefore, we introduce the methods to overcome this severe ITI effect. For instance, the two-dimensional (2D) modulation code that designed based on cross-track data dependent readback. The data pattern such as [1 -1 1]<sup>T</sup> and [-1 1 -1]<sup>T</sup> are forbidden to record onto medium. The rate-5/6 2D modulation code will map the 5 user bits into a 6-bits codeword, which are not contained any forbidden patterns. Furthermore, since the recoded bit is protected from severe ITI effect using modulation code, the middle track can provide a very high reliability. Therefore, we present ITI subtraction to improve upper and lower track performance using data from middle track. Moreover, we also propose an unbalanced track pitch technique, which the middle track can be narrower than upper and lower tracks. The utilization from the high reliability of middle track can improve BER performances both of upper and lower tracks. The reason because the ITI effect that interfere from their sidetracks is reduced by using the properly wider track pitch. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, A two-dimensional coding design for staggered islands bit-patterned media recording(2015-05-07) - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Mitigation of TMR Using Energy Ratio and Bit-Flipping Techniques in Multitrack Multihead BPMR Systems(2017-11-01); - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Spinning disk test study on erase band and write width for shingled magnetic recording(2014-05-07); ; Bai, D.Shingled magnetic recording (SMR) has been predicted as one of the novel technologies to extend the areal density beyond 1 Tb/in<sup>2</sup>. It was widely thought by many researchers that very wide writers could be used for SMR, as it involves corner writing and thus writability would no longer be an issue in SMR. However, in our experimental study, we reveal that there exists an optimal write width for a given writer design due to the erase band limitations. Also we propose the optimal write width for a given shingle track pitch condition. © 2014 AIP Publishing LLC. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Mitigating the Effects of Track Mis-Registration in Single-Reader/Two-Track Reading BPMR Systems(2019-07-01)Bit-recording technologies that can provide areal densities (ADs) [patterned magnetic recording (BPMR) is expected to be one of the new magnetic ADs] of 1 Tera-bit per square inch or higher. To achieve these ADs, the space between tracks must be reduced, bringing them closer and closer together, leading to significant inter-track interference (ITI). Track mis-registration (TMR) or head offset can further degrade overall system performance. To mitigate the effects of ITI and TMR, we propose using a single-reader/two-track reading (SRTR) scheme together with an over-sampling technique on a staggered BPMR system. We also propose a TMR estimation technique based on a readback signal. Here, the readback signal is separated into two sequences, one odd and one even. Then, the energy ratio is calculated using these data sequences. The obtained relationship between the energy ratio and head offset can be utilized to predict the actual head offset occurrence in the reading process. Finally, a pairing of a monic constraint target and an equalizer that accordingly matches each estimated head offset level is adopted to deal with the TMR effect. The SRTR system can provide better bit-error-rate (BER) performance. Moreover, when TMR effects appear in the reading process, our proposed SRTR system with a TMR mitigation technique can yield better BER performance, especially at high head offset levels. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, A study of multiple reads of target track prior to detection for two-dimensional magnetic recording(2015-07-14); Two-dimensional magnetic recording (TDMR) has recently received wide attention as a good candidate for next generation high-density data storage [1]. However, the read-back signal is subject to the combination of inter-track interference (ITI) and inter-symbol interference (ISI). Therefore, a major challenge to apply TDMR depends on the development of two-dimensional signal processing. It is widely studied in a variety of forms, leading to the compromise between detection performance and computation complexity. Some recent works on TDMR channels are presented in [2]-[4]. In [2], performance is enlarged by using 2D iterative detector. As for [3] and [4], multiple readbacks from array-reader were proposed to detect data bit. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, An iterative TMR mitigation method based on readback signal for bit-patterned media recording(2015-11-01); ; Kovintavewat, PiyaOff-track condition or track misregistration (TMR) is one of the most significant problems in the extremely high-density bit-patterned media recording (BPMR) system, since a track pitch becomes narrower. Typically, the TMR can be detected and handled by a servo system; however, it requires some special data to be inserted in the tracks so as to estimate the amount of head offset. Nonetheless, this paper proposes an iterative TMR mitigation method for BPMR systems based on the readback signals. First, we design several pairs of the 2-D asymmetric target and its corresponding 2-D equalizer that match the BPMR channel for each TMR level. Then, we exploit the three adjacent data tracks obtained from the low-density parity-check decoders to estimate the TMR level. Last, a pair of the 2-D asymmetric target and its corresponding 2-D equalizer that is best fit to the estimated TMR level will be used to alleviate the TMR effect in the readback signal for the next global iteration. Simulation results indicate that the proposed system can effectively estimate the TMR level and performs better than the conventional system without a TMR mitigation method, especially when the TMR level is high and/or the position jitter is large. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Soft-output decoding of 2D modulation codes for bit-patterned media recording(2015-07-14); Kovintavewat, P.The two-dimensional (2D) interference is a major impairment in bit-patterned media recording (BPMR) systems because of small bit and track pitches, especially at high recording densities [1]. To mitigate this problem, we introduced 2D modulation codes [2-3], which output only the hard decision, for an uncoded BPMR system (i.e., without error-correction codes). To utilize a rate-4/5 constructive inter-track interference (CITI) code [2] in the coded BPMR system, which employs a low-density parity-check (LDPC) code, we propose the log-likelihood ratio (LLR) algebra implementation in Boolean logic mappings for the CITI coding scheme. Then, this soft CITI coding scheme together with a modified 2D soft-output Viterbi algorithm (2D-SOVA) detector [4] and a LDPC decoder will jointly perform iterative decoding.