Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/tmag.2023.3278377

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/tmag.2022.3146058

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/tmag.2021.3114690

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Authorship：Corresponding author   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/intermag42984.2021.9579866

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Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/tmag.2020.3030300

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Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/tmag.2020.3027253

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Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/tmag.2020.3011163

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Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/tmag.2020.3012156

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/tmag.2021.3113904

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

© 1965-2012 IEEE. The 3-D magnetic recording using the microwave-assisted magnetic recording and a spin-torque oscillator as a reading sensor has been proposed as a candidate of the prospective recording technologies. In our previous research, we have constructed the read/write channel of the envelope model to evaluate a variety of signal processing for the 3-D magnetic recording. In this paper, we apply the low-density parity-check coding and iterative decoding system including turbo equalization to the 3-D magnetic recording channel model with dot position fluctuation and evaluate the bit error rate performance by the computer simulation. The results clarify that the tolerance of dot position fluctuation which 'no errors' is able to be achieved.

DOI： 10.1109/TMAG.2019.2891299

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

© 1965-2012 IEEE. This paper focuses on the shingled magnetic recording (SMR) as the recording system for further high-density hard disk drives. Previously, we applied a log-likelihood ratio (LLR) modulator to the low-density parity check coding and iterative decoding system in SMR to improve the decoding performance. In this paper, we propose a new LLR modulator using neural network. Furthermore, we clarify that the proposed LLR modulator using neural network realizes effective iterative decoding in a read/write channel with pattern-dependent medium noise.

DOI： 10.1109/TMAG.2019.2891711

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Institute of Physics Inc.  

In this article, we propose the detection method of the recorded data pattern by the envelope of the temporal magnetization dynamics of resonantly interacting spin-torque oscillator on the microwave assisted magnetic recording for three-dimensional magnetic recording. We simulate the envelope of the waveform from recorded dots with the staggered magnetization configuration, which are calculated by using a micromagnetic simulation. We study the data detection methods for the envelope and propose a soft-output Viterbi algorithm (SOVA) for partial response (PR) system as a signal processing system for three dimensional magnetic recording.

DOI： 10.1063/1.5006105

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

IEEE The 3-D magnetic recording using microwave-assisted magnetic recording has been proposed as one of the prospective recording technologies which uses a spin-torque oscillator (STO) as a reading sensor as well as a write-assisting device. In the reading process using an STO, the reproducing waveform is given as temporal dynamics of magnetization. We simulate the envelope of the waveform from recorded dots with the staggered magnetization configuration, which are calculated by using a micromagnetic simulation. We propose an envelope demodulation using two temporal magnetization dynamics from dual STO, and evaluate the bit error rate (BER) performance for partial response maximum likelihood system by the computer simulation. The result shows that our proposed system provides the signal-to-noise ratio improvement of 2.7 dB at the BER of 10⁻⁴.

DOI： 10.1109/TMAG.2018.2829220

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

IEEE In recent years, shingled magnetic recording (SMR) has attracted attention as a new recording system of the hard disk drives. Although SMR can realize narrow track by overwriting data track like tile roofing, it has remarkable performance deterioration due to the influence of inter-track interference. Therefore, the performance improvement of the low-density parity-check (LDPC) coding and iterative decoding system using the sum-product decoding is required. In this paper, we propose the LDPC encoding and iterative decoding system with the log-likelihood ratio modulator and show the error floor is eliminated and improvement of signal-to-noise ratio to achieve the error free is obtained in the SMR under an areal recording density of 4 Tbits/in$²$ specification for the channel bit sequence coded by run-length limited and LDPC encoders by computer simulation. Therefore, the channel bit is composed bit about five magnetic grains.

DOI： 10.1109/TMAG.2018.2833167

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

The shingled magnetic recording (SMR) system is influenced by not only jitter-like medium noise from adjacent bits in the down-track direction but also intertrack interference (ITI) from the adjacent tracks. In this paper, we investigate the relationship between the recording pattern and the decoding reliability by classifying the log-likelihood ratio at the a posteriori probability decoder output according to the recording patterns under an SMR R-W channel specification of 4 Tb/in(2) by computer simulation. The result shows that the decoding reliability for the recording pattern "010" heavily affected by transition jitter is the lowest and little improved even if the influence of ITI is mitigated by a 2-D finite-impulse response filter.

DOI： 10.1109/TMAG.2017.2721428

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Two-dimensional magnetic recording (TDMR), which combines shingled magnetic recording (SMR) with 2-D signal processing attracts attention from the hard disk drive industry. SMR is a magnetic recording system in order to increase the track density by writing tracks without the guard band. Therefore, the influences of writing and reading intertrack interferences (ITIs) deteriorate the quality of reproducing waveforms. Additionally, degradation of track due to overwriting and crosstalk from the adjacent tracks due to the width of reader sensitivity. The equalization using 2-D finite impulse response filter for the waveforms from three adjacent tracks is proposed as a method to reduce the influence of reading ITIs. In this paper, we evaluate the bit aspect ratio (BAR) in TDMR read/write channel under a specification of 4 Tb/in(2) using bit error rate of the low-density parity-check (LDPC) coding and iterative decoding system obtained by computer simulation. The results show that the suitable BAR in array head reading is 2.0.

DOI： 10.1109/TMAG.2017.2701355

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Two-dimensional magnetic recording (TDMR) by shingled magnetic recording (SMR) draws attention as a next generation technology to increase the recording density in hard disk drive (HDD). It is shown that the two-dimensional finite impulse response (2D-FIR) filter provides gain the reproducing waveforms from an array head with 3 readers in the TDMR under a specification of 4 Tbit/inch.(2) We evaluate the effect of the intertrack interference (ITI) reduction by 2D-FIR using the correlation between the real FIR filter output and the partial response class-I (PR1) signal corresponding to recording sequence by the computer simulation. The results show that the 2D-FIR filter is effective to mitigate ITI and improves the signal-to-noise ratio at the discriminate point by about 0.6 dB. (C) 2017 Author(s).

DOI： 10.1063/1.4977548

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

This paper proposes a utilization of multiple read heads to predict and correct a track mis-registration (TMR) in bit-patterned media recording (BPMR) based on the readback signals. We propose to use the signal energy ratio between the upper and lower tracks from multiple read heads to estimate the TMR level. Then, a pair of two-dimensional (2D) target and its corresponding 2D equalizer associated with the estimated TMR will be chosen to correct the TMR in the data detection process. Numerical results show that the proposed system can achieve a very high accuracy of TMR prediction, thus performing better than the conventional system, especially when TMR is severe. (C) 2016 Author(s).

DOI： 10.1063/1.4972801

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

The 2-D magnetic recording (TDMR) by shingled magnetic recording (SMR) draws attention as a technology to increase the recording densities in a hard disk drive. The magnetization pattern is curved by the write field at the corner of the writer in SMR, and the information to read/write (R/W) channel performance is feared. Therefore, it is possible that the bit error rate performance is improved by fitting the reader sensitivity to the bit shape. In this paper, we evaluate the effect of reader sensitivity rotation in the TDMR R/W channel with head skew under a specification of 4 wTb/in(2) by computer simulation, applying the low-density parity-check coding and the iterative decoding system with the 2-D finite impulse response filter. The results show that the rotated reader sensitivity fits the recorded bit magnetization shape, and the error-free skew range increases to -3 degrees similar to 6 degrees. Therefore, the reader sensitivity rotation is considered to be an effective way to improve the skew margin in the TDMR system.

DOI： 10.1109/TMAG.2016.2531088

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

The move from traditional single-track magnetic recording to two-dimensional magnetic recording (TDMR) with squeezed tracks and multiple readers opens up new design degrees of freedom beyond the track pitch and bit-aspect ratio, including the widths, spacing, and crosstrack positions of the readers. In this paper, we present a systematic method for determining the combination of multi-reader geometry, track pitch, and bit-aspect ratio that maximizes the areal density of a TDMR system using single-track detectors. The method combines realistic modeling of the medium and write/read processes, advanced signal detection, and information-theoretic tools. For the particular head and medium we consider, the two-reader geometry that maximizes areal density with zero skew and zero misregistration was found to use different-sized readers (the smaller having a full-width at half-maximum width, i.e., 96% of the track pitch and the larger having a width, i.e., 148% of the track pitch) with significant overlap in the crosstrack direction (centers spaced by one eighth of the track pitch). The optimal bit-aspect ratio was 2.2. At the optimal operating point, the information rate per coded bit is 0.8.

DOI： 10.1109/TMAG.2015.2483593

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Image Information and Television Engineers  

Tape systems experience large speed variations compared to disk systems, and therefore, it is necessary to design a stable timing recovery scheme that can operate under a low signal-to-noise ratio (SNR) condition. In such low SNR scenarios, the decision error made by the detector often results in a phase-locked loop circuit losing track of the correct signal. This phenomenon is often called the loss-of-lock (LOL) phenomenon. In order to mitigate the LOL issue, soft information from the soft output Viterbi algorithm decoder is used to control the feedback in the timing recovery loop. Therefore, a timing recovery method for high-density tape storage system is studied in this paper. By applying this new method to the read back signal from the actual tape drive, it is verified that the negative effect of misdetection due to unreliable decisions from the detector can be compensated, with only a minor increase in implementation complexity.

DOI： 10.3169/mta.4.296

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

2-D magnetic recording (TDMR) exploits 2-D signal processing using the waveforms reproduced by array head from the intended and adjacent tracks to mitigate the effects of intertrack interference. However, an array head has the issue on the degradation of bit error rate (BER) performance due to head skew. In this paper, we evaluate the BER performance of TDMR R/W channel with head skew under a specification of 4 Tbit/in(2) employing low-density parity check coding and iterative decoding system using a 2-D finite-impulse response filter by computer simulation. The results show that our system can achieve the reliable BER performances by appropriately setting the reader scanning positions at the head skew angle between 0 degrees and 3 degrees.

DOI： 10.1109/TMAG.2015.2445372

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

A timing recovery method for a high-density tape storage system is studied in this paper. Since tape systems suffer from large speed variations compared with disk systems, the design of a stable timing recovery scheme that can operate under low signal-to-noise ratio (SNR) conditions is important. In such low SNR scenarios, decision errors made by the detector occasionally cause the phase-locked loop circuit to lose track of the correct signal, which is often called the loss-of-lock (LOL) phenomenon. In order to mitigate the LOL issue, soft information from the Viterbi detector is utilized. It is clarified that the negative effect of unreliable decisions from the detector can be compensated for by dynamically controlling the feedback gain of the timing recovery loop as a function of decision reliability. It is shown that the LOL rate performance can be improved by this approach, with only a minor increase in the implementation complexity.

DOI： 10.1109/TMAG.2015.2439059

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The two-dimensional magnetic recording (TDMR) exploits two-dimensional signal processing using the neighboring read-back waveforms. We allocate dual readers for the intended tracks and evaluate the effects of head skew angle on the bit error rate performance in partial response class-I maximum likelihood system with a two-dimensional finite impulse response filter using two read-back waveforms under TDMR R/W channel specifications of 4 Tbit/in.(2). The results show that the effect of positive skew angle is larger than that of negative skew angle, and the center of skew angle should be shifted to minus direction. (C) 2015 AIP Publishing LLC.

DOI： 10.1063/1.4906965

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Two-dimensional magnetic recording is affected by the inter-track interference (ITI) from the adjacent tracks. We investigate the improvement of partial response maximum likelihood (PRML) systems with signal dependent noise predictor (SDNP) in the bit error rate performance. The systems reduce the influence of ITI by two dimensional finite impulse response filter using the waveforms reproduced by triple readers from the adjacent tracks. The results show that the SDNP provides larger improvement to PR(2,6,1)ML system compare with PR1ML system. (c) 2015 AIP Publishing LLC.

DOI： 10.1063/1.4908145

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

This paper presents the results of a comprehensive study of the shingled writing process and various signal processing and data detection approaches applied to the readback waveforms. The recording simulations include realistic head fields, a random granular media, magnetostatic and exchange interactions, and a READ head sensitivity function. Readback waveforms are examined in both one and two dimensions in terms of signal characteristics (linear and nonlinear), noise behavior (stationary and signal-dependent), and intertrack interference. Different equalization and detection approaches are compared and about a 10% density gain is reported for such 2-D magnetic recording compared with traditional single-track recording. These gains depend strongly on the number of readers, the reader positioning, and the reader width.

DOI： 10.1109/TMAG.2014.2356455

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE  

Copyright © 2016 by ITE Transactions on Media Technology and Applications (MTA). Tape systems experience large speed variations compared to disk systems, and therefore, it is necessary to design a stable timing recovery scheme that can operate under a low signal-to-noise ratio (SNR) condition. In such low SNR scenarios, the decision error made by the detector often results in a phase-locked loop circuit losing track of the correct signal. This phenomenon is often called the loss-of-lock (LOL) phenomenon. In order to mitigate the LOL issue, soft information from the soft output Viterbi algorithm decoder is used to control the feedback in the timing recovery loop. Therefore, a timing recovery method for high-density tape storage system is studied in this paper. By applying this new method to the read back signal from the actual tape drive, it is verified that the negative effect of misdetection due to unreliable decisions from the detector can be compensated, with only a minor increase in implementation complexity.

DOI： 10.3169/mta.4.296

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

The two-dimensional magnetic recording (TDMR) by shingled magnetic recording needs two-dimensional (TD) signal processing using the multiple read-back waveforms. In this paper, to allocate dual readers (reader 1 and 2) for the intended tracks, we evaluate the bit error rate (BER) performance of a low-density parity-check coding and iterative decoding system with a TD-finite impulse response equalizer under TDMR R/W channel specifications of 4 Tb/in(2). Here, the TDMR R/W channel is modeled using a discretized granular medium and the writing process based on a slope model considering the media switching field angle given by the Stoner-Walfarth reversal mechanism. The result shows that to affect the good BER performance, the reader 1 should be placed slightly toward the next track from the center of the home track, and the reader 2 should be placed around the boundary between the home and following tracks.

DOI： 10.1109/TMAG.2014.2318335

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

In this paper, we investigate the influence of the writing and reading intertrack interferences (ITIs) in terms of bit aspect ratio (BAR) in shingled magnetic recording by computer simulation using a read/write model which consists of a writing process based on Stoner-Wohlfarth switching asteroid by a one-side shielded isosceles triangular write head and a reading process by an around shielded read head for a discrete Voronoi medium model. The results show that BAR should be 3 to reduce the influence of writing and reading ITIs, media noise, and additive white Gaussian noise in an assumed areal density of 4.61Tbpsi. (C) 2014 AIP Publishing LLC.

DOI： 10.1063/1.4866393

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

Bit-patterned medium (BPM) is one of the promising approaches for ultra-high density magnetic recording systems. However, BPM requires precise write synchronization, and exhibits write-errors due to insufficient write field gradient, medium switching field distribution (SFD), demagnetization field from adjacent islands, and island position variation. In this paper, an iterative decoding system using a non-binary low-density parity-check (LDPC) code is considered for a BPM R/W channel with write-errors at an areal recording density of 2 Tbit/inch(2) including the coding rate loss. The performance of the iterative decoding system using the non-binary LDPC code over the Galois field GF(2(8)) is evaluated by computer simulation, and it is compared with the conventional iterative decoding system using a binary LDPC code. The results show that the non-binary LDPC system has a larger write margin than the binary LDPC system.

DOI： 10.1587/transele.E96.C.1497

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Other Link： http://dblp.uni-trier.de/db/journals/ieicet/ieicet96c.html#journals/ieicet/NakamuraOOAM13

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

A neuro intertrack interference canceller (neuro-ITIC) is proposed to diminish the influences of ITI and jitter-like medium noise for two-dimensional magnetic recording (TDMR) by shingled magnetic recording. The bit error rate (BER) performance of a low-density parity-check coding and iterative decoding system including a generalized partial response class-I channel with the neuro-ITIC is also obtained via computer simulation using a read/write channel model under TDMR specifications of 4 Tb/in(2), and it is compared to those for a two-dimensional neural network equalizer (2D-NNE) and an ITI canceller (ITIC) with a one-dimensional finite impulse response equalizer (1D-FIRE). It is clarified that the BER performance for the neuro-ITIC is far superior to those for the 2D-NNE and the ITIC with the 1D-FIRE.

DOI： 10.1109/TMAG.2013.2242437

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

In this paper, the influence of the intertrack interference (ITI) at writing in shingled magnetic recording (SMR) as well as at reading is examined using a read/write model based on recording on a medium composed of discrete Voronoi diagram by a triangular writer with trailing and one-side shields. Two kinds of ITI's at writing which affect the magnetic grains on the track currently being written and the previously recorded track are shown. One is that a part of signal on the previously recorded track remains on the current track due to lack of writing ability of writer. Another is that a part of signal is erased by the next-track writing. The effects are caused from the adjacent tracks at writing. Additionally the ITI at reading deteriorates the read-back waveform. Consequently these ITI's bring the decoding errors. The results by computer simulation using above R/W model show that the decoding errors occur in the low density parts of track which were originally considered to be hard to make errors.

DOI： 10.1109/TMAG.2013.2242439

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Two-dimensional magnetic recording (TDMR) by shingled magnetic recording (SMR) is one of the most promising technologies for realizing high areal densities. The read/write (R/W) channel model based on a discrete Voronoi model is relatively easily implemented to evaluate the performance of signal processing for TDMR. The nonbinary low-density parity-check (LDPC) coding and iterative decoding system provides the better performance compared with the conventional binary LDPC coding system. Furthermore, a two-dimensional equalizer (2D-EQ) can mitigate the influence of the intertrack interference (ITI) in TDMR. In this paper, the symbol-by-symbol turbo equalizer which consists of a symbol-by-symbol a posteriori probability (APP) decoder for a generalized partial response class-I (GPR1) channelwith a 2D-EQ and a sum-product (SP) decoder for a nonbinary LDPC coder overGalois field GF (2(8)) of is evaluated by computer simulation at an areal recording density of 4.12 Tbit/in(2). The result shows that the symbol-by-symbol turbo equalizing system provides an SNR improvement of about 3.7 dB over the bit-by-bit turbo equalizing system.

DOI： 10.1109/TMAG.2013.2245863

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

A 2-D magnetic recording (TDMR) by shingled magnetic recording (SMR) is one of the most promising technologies for realizing ultra-high areal densities. We have developed the discretized granular medium model with nonmagnetic grain boundaries and the simple writing process considering intergranular exchange fields and magnetostatic interaction fields between grains on the discrete Voronoi model for TDMR. In this paper, the bit-error rate (BER) performance of the iterative decoding system using a nonbinary low-density parity-check (LDPC) code over Galois field GF(q) with the 2-D finite-impulse-response equalizer (2D-FIRE) is obtained via computer simulation using an R/W channel model employing the writing process under TDMR specifications of 4.12 Tb/in(2), and it is compared to that with the 1-D FIRE (1D-FIRE). The results show that the BER performance of the nonbinary LDPC coding and iterative decoding system with the 2D-FIRE is better than that with the 1D-FIRE.

DOI： 10.1109/TMAG.2012.2220532

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communication, Engineers, IEICE  

The previously-proposed model of the writing process in TDMR is modified based on the Stoner-Wohlfarth reversal mechanism. The BER performance for a neuro-ITI canceller is obtained via computer simulation using the R/W channel model based on the writing process, and it is compared to those for well-known TDMR equalization techniques. Copyright © 2013 The Institute of Electronics, Information and Communication Engineers.

DOI： 10.1587/transele.E96.C.1504

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Other Link： http://dblp.uni-trier.de/db/journals/ieicet/ieicet96c.html#journals/ieicet/YamashitaONOGM13

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

It is expected for the nonbinary low-density parity-check (LDPC) coding and iterative decoding system to introduce the turbo equalization in order to enhance the error correction ability in the bit-patterned medium (BPM) R/W channel. In this paper, we investigate the effect of the turbo equalization on the bit-error rate (BER) performance of nonbinary LDPC coding and iterative decoding system over Galois filed GF(2(8)) in BPMR/W channel with write-error at an areal recording density of 2 Tbit/inch(2) considering the coding rate loss. The performance of turbo equalization using the nonbinary LDPC coding and iterative decoding system is evaluated by computer simulation, and it is compared to that without turbo equalization. The results show that the nonbinary LDPC and iterative decoding system with the turbo equalization has the larger write-margin compared to that without turbo equalization.

DOI： 10.1109/TMAG.2012.2194989

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Modeling of a simple writing process considering intergranular exchange fields and magnetostatic interaction fields between grains is studied for two-dimensional magnetic recording (TDMR). A new designing method of a two-dimensional neural network equalizer with a mis-equalization suppression function (2D-NNEMS) for TDMR is also proposed. The bit-error rate (BER) performance of a low-density parity-check coding and iterative decoding system with the designed 2D-NNEMS is obtained via computer simulation using a read/write channel model employing the proposed writing process under TDMR specifications of 4 Tb/in(2), and it is compared with those for one- and two-dimensional finite impulse response equalizers (FIREs). It is clarified that the BER performance for the designed 2D-NNEMS is far superior to those for the FIREs.

DOI： 10.1109/TMAG.2012.2194988

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

A simple writing process considering magnetic clusters due to exchange coupling between grains is studied for two-dimensional magnetic recording. The bit error rate (BER) performance of a low-density parity-check coding and iterative decoding system with a two-dimensional neural network equalizer (2D-NNE) that can diminish the influences of jitter-like medium noise and inter-track interference is obtained using a read/write channel model based on the proposed writing process, and it is compared with those for one-and two-dimensional finite impulse response equalizers (FIREs). It is clarified that the BER performance for the 2D-NNE is far superior to those for the FIREs. (C) 2012 American Institute of Physics. [doi:10.1063/1.3680535]

DOI： 10.1063/1.3680535

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

The write-margin of the iterative decoding systems for the binary and non-binary low-density parity-check (LDPC) codes are studied in the magnetic recording system using a bit-patterned medium (BPM) R/W channel with write-errors caused by the write-head field gradient, the media switching field distribution (SFD), the magnetization fields from adjacent islands, and the island position deviation. The performances of iterative decoding systems using the binary and non-binary LDPC codes are evaluated by computer simulation at an areal recording density of 2 Tb/inch(2). The results show that the non-binary LDPC coding and iterative decoding system improves the write-margin compared with the binary LDPC system. Furthermore it is clarified that in order to obtain the sufficient write-margin, it is important to suppress the influence of the demagnetization fields from adjacent islands.

DOI： 10.1109/GLOCOM.2012.6503609

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

The magnetic recording system using a bit-patterned medium (BPM) has serious problems such as the need of the precise write-synchronization to correctly write the recording sequence on each intended island and the write-errors caused by the insufficient write field gradient, the medium switching field distribution (SFD), the demagnetization fields from adjacent islands, and the island position variation. In this paper, the influences of the SFD and the demagnetization fields from adjacent islands on the write-margin of the low-density parity-check (LDPC) coding and iterative decoding system is studied in the BPM R/W channel with write-errors at an areal recording density of 2 Tbit/inch(2). It is clarified that in order to obtain the sufficient write-margin, it is important to suppress the influence of the demagnetization fields from adjacent islands.

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Other Link： http://dblp.uni-trier.de/db/conf/isita/isita2012.html#conf/isita/NakamuraOOAM12

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

In this paper, the iterative decoding system using the nonbinary low-density parity-check (LDPC) code is studied in the magnetic recording system using a bit-patterned media (BPM) R/W channel affected by the write head field gradient, the media switching field distribution (SFD), the demagnetization field from adjacent dots, and the dot position deviation in an areal recording density of 2 Tb/in(2). The performance of iterative decoding system using the nonbinary LDPC code over Galois field of GF(2(8)) is evaluated by the computer simulation, and it is compared with the conventional iterative decoding system using the binary LDPC code. The results show that the nonbinary LDPC system provides better performance compared with the binary LDPC system.

DOI： 10.1109/TMAG.2011.2147766

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

The performance of an iterative decoding system is evaluated in shingled magnetic recording (SMR). The medium model is made by a discrete Voronoi model, and the 2-D sensitivity function of reader is used to obtain the reproducing waveform. As the sensitivity function extends to adjacent tracks, intertrack interference (ITI) deteriorates the signal detection system. In order to recover the intrinsic performance, it is required to reduce the influence of ITI to the system. Then, the ITI canceller is employed to combat ITI for the iterative decoding system, and the performance is evaluated by computer simulation. The results show that the introduction of ITI canceller improves the bit-error-rate performance in SMR system.

DOI： 10.1109/TMAG.2011.2158075

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

An accurate medium modeling method of discretized granular medium with non-magnetic grain boundaries using a discrete Voronoi diagram is proposed for two-dimensional magnetic recording. A simple closed-form representation of a double-shielded reader sensitivity function is also proposed for modeling the reading process. Moreover, a two-dimensional neural network equalizer (2D-NNE) is proposed to mitigate the influence of intertrack interference and jitter-like medium noise. The bit-error rate performance of partial response class-I maximum likelihood (PR1ML) system with the 2D-NNE is obtained by computer simulation based on the proposed read/write channel model. The performance is far superior to that of PR1ML system with a two-dimensional finite impulse response equalizer.

DOI： 10.1109/TMAG.2011.2157808

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

垂直磁気記録再生系におけるポストプロセッサを伴うPRML(partial response maximum likelihood)方式のためのニューラルネットワーク等化器について検討している.まず,高レベルの識別点雑音の発生を抑圧するニューラルネットワーク等化器(NNE)の設計法を提案する.本手法では,分散遺伝的アルゴリズムと誤差逆伝搬法を組み合わせたハイブリット分散遺伝的アルゴリズムに用いる適応度に識別点雑音の頻度分布形状を調節する項を導入することにより高レベルの識別点雑音の抑圧とNNEの簡単化を図る.次いで,PR1ML方式の等化器としてこの雑音抑圧機能をもつNNEを用いた,ポストプロセッサを伴うPR1ML方式のビット誤り率特性を求め,従来の雑音抑圧機能をもたないNNEを用いた場合及び従来のトランスバーサルフィルタを用いた場合と比較検討している.その結果,提案方式は従来方式,トランスバーサルフィルタを用いた方式に比べて良好な特性を示すことが明らかとなった.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

The neural network equalizer (NNE) matched to recording code is proposed to reduce the influence of interpixel interference in holographic data storage (HDS). A searching method is proposed to proceed simultaneously with the search of a conversion table of the 5-9 recording code and the search of simplified NNE by using hybrid genetic algorithm. Furthermore, the bit error rate performance of HDS system is obtained. The result shows that the proposed method is superior in the performance to the conventional method. (C) 2011 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.50.09MB05

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

In this paper, we propose a new method to estimate and effectively reduce the effect of thermal asperity (TA) in the perpendicular magnetic recording (PMR) channels with the state trellis. The TA is estimated from the state trellis, then its average is used to modify the equalized signal entering the Viterbi detector. For the partial response (PR) targets with DC component, the proposed method with a maximum-likelihood detector can improve the bit error rate performance by more than an order of magnitude when TA occurs and degrades when the giant magneto-resistive (GMR) nonlinearity and base line wander (BLW) effects are present. Unlike the previous studies, this method allows the use of PR targets with DC component under the presence of TA.

DOI： 10.1587/transele.E94.C.1472

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Other Link： http://dblp.uni-trier.de/db/journals/ieicet/ieicet94c.html#journals/ieicet/SuppakhunSONO11

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

Shingled magnetic recording attracts much attention as a new recording system for hard disk drive to make the narrower track than the writer-track-width. However, the issue for reading by a wider reader than the track width on the media remains, and the inter-track interference (ITI) from adjacent tracks causes the performance deterioration. To recover the performance, in this paper, we propose an ITI canceller for the reproduced waveform from shingle-recorded tracks, and evaluate the performance of the PRML channel. (C) 2011 Published by Elsevier B.V. Selection and/or peer-review under responsibility of the Organising Committee of the 9th Perpendicular Magnetic Recording Conference

DOI： 10.1016/j.phpro.2011.06.112

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Elsevier B.V.  

The neural network equalizer (NNE) for the generalized partial response maximum likelihood (GPRML) system with a postprocessor in perpendicular magnetic recording is studied. First, a new designing method of NNE is proposed for suppressing frequency of a high-level noise at the discrimination point which degrades the bit error rate (BER) performance of the GPRML system with a post-processor. Then, the BER performance of GPR class-1 ML system with a post-processor using the NNE is obtained and compared with that using a conventional transversal filter as an equalizer. The result shows that the gain of the former over the latter is about 0.6 dB at a BER of 10-5. © 2011 Published by Elsevier B.V.

DOI： 10.1016/j.phpro.2011.06.111

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Elsevier B.V.  

We evaluate the performance of the write-margin for the low-density parity-check (LDPC) coding and iterative decoding system in the bit-patterned media (BPM) R/W channel affected by the write-head field gradient, the media switching field distribution (SFD), the demagnetization field from adjacent islands and the island position deviation. It is clarified that the LDPC coding and iterative decoding system in R/W channel using BPM at 3 Tbit/inch 2 has a write-margin of about 20%. © 2011 Published by Elsevier B.V.

DOI： 10.1016/j.phpro.2011.06.113

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Elsevier B.V.  

Shingled magnetic recording attracts much attention as a new recording system for hard disk drive to make the narrower track than the writer-track-width. However, the issue for reading by a wider reader than the track width on the media remains, and the inter-track interference (ITI) from adjacent tracks causes the performance deterioration. To recover the performance, in this paper, we propose an ITI canceller for the reproduced waveform from shingle-recorded tracks, and evaluate the performance of the PRML channel. © 2011 Published by Elsevier B.V.

DOI： 10.1016/j.phpro.2011.06.112

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

The neuro-interpolator (NI) integrating the interpolator with neural network equalizer is proposed to reduce the influence of interpixel interference in holographic data storage. The simplification of NI is performed by using a hybrid genetic algorithm based on a new mutation method. The bit error rate performance of the simplified NI is superior to that of the interpolator alone. Furthermore, the number of connections in the simplified NI is reduced to about half of that obtained by using a conventional mutation method. (C) 2010 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.49.08KD10

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

本論文では,NLTS(nonlinear transition shift)を伴う垂直磁気記録再生系において,誤りパターンとパリティ検査符号を組み合わせたポストプロセッサを提案し,その性能評価を行っている.まず,記録補償器を備えたPRML方式の記録再生系について述べ,NLTS,記録補償が性能に与える影響とその誤りの特徴について述べている.次いで,その誤りの特徴とパリティ検査符号を組み合わせたポストプロセッサについて述べ,ポストプロセッサを用いた方式の性能比較を行った.その結果,提案した方式はAR(autoregressive)チャネルを用いた方式と比べて良好な特性を示すことが明らかとなった.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

本論文では,サーマルディケイを伴う垂直磁気記録再生系におけるGPRML(Generalized Partial Response Maximum Likelihood)方式のためのニューラルネットワーク等化器の簡単化について検討している.まず,雑音の白色化機能を備える簡単化ニューラルネットワーク等化器(NNE)の設計法を提案している.本手法は,ハイブリッド遺伝的アルゴリズムとレビンソン・ダービンアルゴリズムの交互繰返し学習により得られたNNEにおいて,寄与の小さい結合荷重をもつ結合を間引くことに基づいている.次いで,この簡単化NNEを用いたGPR1ML方式(GPR1ML-NNE)とPR1ML方式(PR1ML-NNE)のビット誤り率の経時変化特性を求め,等化器として従来のトランスバーサルフィルタ(TF)を用いるGPR1ML方式(GPR1ML-TF)の特性と比較検討している.その結果,GPR1ML-NNE,PR1ML-NNEはGPR1ML-TFに比べてともに良好な特性を示すことが明らかとなった.

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

The neuro-interpolator (NI) integrating an interpolator with a neural network equalizer in holographic data storage is proposed to reduce the influence of interpixel interference due to the aperture restriction which limits the effective recording area on the holographic medium. The simplification of NI is performed by using a hybrid genetic algorithm based on a new mutation method introducing a pruning probability, and its bit error rate (BER) performance is studied by computer simulation. The results show that the BER performance of simplified NI is superior to that of the interpolator alone. Furthermore, the number of connections in the simplified NI is reduced to about half of that obtained by using a conventional mutation method. In addition, the proposed mutation method shows the slightly-improved performance over the conventional one.

DOI： 10.11485/itetr.34.20.0_67

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

In this paper, low-density parity-check (LDPC) coding and iterative decoding system is studied in the magnetic recording system using a bit-patterned medium (BPM). The magnetic recording system using BPM has a serious problem of requiring precise write synchronization to correctly write the recording sequence on each intended island. In this paper, an error locator using the parity-check matrix of LDPC code is utilized to curb the influence of write error on the iterative decoding process. The performance of the proposed system with the error locator is evaluated by computer simulation for magnetic recording system using BPM with synchronization write error at a recording density of 2 Tb/in(2) and it is compared with a conventional Reed-Solomon (RS) encoding and decoding system. The results show that the proposed system provides better performance.

DOI： 10.1109/TMAG.2009.2022331

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

サーマルディケイを伴う垂直磁気記録に対するGPRML (Generalized Partial Response Maximum Likelihood)方式の性能評価を行っている.熱安定性の異なる三つのCoPtCr-SiO_2垂直磁気記録媒体の再生波形振幅の経時変化特性にフィットする近似式を求めた.この近似式より,ユーザデンシティを変えた場合の実測では得がたい長期間後の再生波形減衰量を求めることができる.これより, RLL (Run-Length-Limited)符号として128/130(0, 16/8)符号を用いた場合のGPRML方式の長期間後の誤り率特性及びユーザデンシティを変えた場合の誤り率特性を求めた.その結果,いずれの媒体においても,ユーザデンシティが高くなるほどサーマルディケイの影響は小となり,誤り率特性は良好となる.特に,熱安定性の劣る媒体を用いた場合には,経過時間が長くなるほど誤り率特性の改善が大となることが明らかとなった.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

A new design method of the simplified neural network equalizer (NNE) with the noise whitening function for a generalized partial response (GPR) channel is proposed. The long-term bit error rate performance of GPR class-I maximum likelihood (GPR1ML) system employing NNE in perpendicular magnetic recording (PMR) channel with thermal decay is also obtained by computer simulation using our thermal decay model for a CoPtCr-SiO2 PMR medium with KuV/kT = 60. The performance of GPR1ML system with NNE (GPR1ML-NNE) is superior to that of GPR1ML with a transversal filter equalizer. The PR1ML system using a noise whitening NNE and a two-state Viterbi detector provides almost equivalent performance to that of GPR1ML-NNE having a 16-state detector.

DOI： 10.1109/TMAG.2008.2002425

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

In this paper, a low-density parity check (LDPC) coding and iterative decoding system is studied in perpendicular magnetic recording (PMR) with a bit-patterned medium. We propose the efficient iterative decoding algorithm attenuating reliability information, and evaluate the sector error rate (SER) performance of the LDPC coding and iterative decoding system by R/W computer simulations. It is clarified that the proposed systems provide better SER performances than that of the conventional system at an areal density of 1 Tbit/in(2) and can also prevent the error floor which appears in the performance of conventional system. (C) 2008 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.jmmm.2008.08.024

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Nonlinear transition shift (NLTS) influences the performance of PRML channels in perpendicular magnetic recording. For NLTS, it is thought that write pre-compensation is useful to write the transition at the intended position. In this paper, we study the influence of NLTS on the BER performance of GPRML channels and show the appropriate amount of pre-compensation for GPRML channels both with and without a post-processor (PP) to achieve better BER performance. The results show that the widening the shortest bit length by NLTS brings the BER improvement to GPRML channel and the write pre-compensation is useful for a GPRML channel with PP. (C) 2008 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.jmmm.2008.08.028

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

In this paper, we study not only the new constructive inter-track interference (CITI) code based on the equalized level but also Viterbi detection algorithm taking into account the ITI from adjacent tracks for the perpendicular magnetic recording channel without a differentiator of two-track model. Although the investigation of this paper was not practical but theoretical, the result shows that the permissible percentage of ITI for conventional Viterbi detection to attain better performance compared with the case of single track is 26%, while the percentage for the proposed one is improved up to 50%. Further investigation has to be required under a more realistic system and moreover may be expanded into patterned media perpendicular magnetic recording. (C) 2008 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.jmmm.2008.08.026

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The bit-error rate (BER) performance of the generalized partial response maximum likelihood with autoregressive (GPRML-AR) channel model system in perpendicular magnetic recording (PMR) channel with thermal decay is obtained. The 128/130(0,16/8) run-length-limited (RLL) code is used as a recording code. The GPR channel consists of the PR1 channel followed by the reduction circuit of predicted noise. The BER performance is evaluated by computer simulation using a thermal decay model. The model has been obtained by using an approximate equation that represents amplitude degradation of the reproducing waveform with elapsed time based on the experimental data for CoPtCr-SiO(2) PMR media. The Viterbi detector with an AR channel model is employed. Furthermore, long-term degradation of the required SNR to achieve a BER of 10(-4) with elapsed time is obtained and the performance is compared with that of PR1ML system. The results show that the poorer the thermal stability of the medium becomes, the larger the SNR gain of the GPR1ML-AR system over the PR1ML system becomes. The SNR gain also increases with elapsed time. (C) 2008 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.jmmm.2008.08.025

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

In this paper, a new burst detection method using the check matrix of low-density parity-check (LDPC) code is proposed. The burst detection for the bit flipping burst-like signal degradation which the conventional burst detection using a reproducing waveform, an equalizer output, an a posteriori probability (APP) decoder output and so on cannot detect is studied. The performance of the LDPC coding and iterative decoding system with the proposed burst detector is evaluated by computer simulation for a perpendicular magnetic recording channel with bit flipping burst-like signal degradation, and it is compared with that of the RS encoding and decoding system using the erasure correction. The results show that the LDPC coding and iterative decoding system with our burst detector shows the better performance and has the resistance to the bit flipping burst-like signal degradation of about 1500 bits.

DOI： 10.1109/TMAG.2008.2002424

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

本論文では,バーストを伴う垂直磁気記録再生系において,4096バイト/セクタのロングセクタを想定してLDPC符号の性能評価を行っている.まず,バースト検出器を適用したLDPC符号化・繰返し復号化方式の記録再生系,バースト検出器,及びバースト誤りによる誤り伝搬を抑制するための繰返し復号器について述べている.次いで,計算機シミュレーションにより所定のデータを誤りなく復号するための所要SN比とバースト長の関係を求め,バースト情報を用いたLDPC符号化・繰返し復号化方式とRS符号を用いた消失誤り訂正を採用した方式の性能比較を行った.その結果,提案したLDPC符号化・繰返し復号化方式はRS符号を用いた消失誤り訂正に比べて,より低いSN比で約2000ビットのバースト耐性が得られることが明らかとなった.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, a burst detection scheme using a parity check matrix of LDPC code is described for the perpendicular magnetic recording using a bit-pattered medium. It is assumed that the burst-like bit-flipping occurs due to missing the write synchronization. The phenomenon cannot be detected as a signal decay and significantly degrades the performance of the LDPC coding and iterative decoding system. Therefore, a good alternative detector is required in order to keep the performance. The LDPC coding and iterative decoding system is evaluated by the computer simulation in a perpendicular magnetic recording channel using a bit-patterned medium with the burst-like bit-flipping. It is clarified that the LDPC coding and iterative decoding system with a burst detector has the resistance to a burst-like bit-flipping of 200 bits.

DOI： 10.1109/ISITA.2008.4895390

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

The long-term bit error rate (BER) performance of partial response maximum likelihood (PRML) system using an adaptive equalizer in a perpendicular magnetic recording (PMR) channel with thermal decay is studied. A thermal decay model based on the experimental data giving the amplitude change of reproducing waveforms with the elapsed time for CoPtCr-SiO2 PMR medium is obtained. The BER performance of PRIML channel for the 16/17(0,6/6) run-length-limited (RLL) code is evaluated by computer simulation using the model. The relationship between the ratio R-J of the jitter-like media noise power to the total noise power at the reading point and the required SNR to achieve a BER of 10(-4) is also obtained and the performance is compared with that of the conventional equalization. The results show that the significant improvement in SNR by utilizing the adaptive equalization is recognized over all R-J compared with the conventional equalization.

DOI： 10.1093/ietele/e90-c.8.1583

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

The neural network equalization for polytopic multiplexing holography is studied to reduce interpixel interference. The bit error rate performance of the bilinear or bicubic interpolator followed by a neural network as an equalizer is obtained by computer simulation. The results show that the neural network equalizer provides an SNR improvement of about 1.0 dB over conventional equalization.

DOI： 10.1093/ietele/e90-c.8.1612

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

The long-term bit error rate (BER) performance of partial response maximum likelihood (PRML) system in a perpendicular magnetic recording (PMR) channel with thermal decay is studied. A thermal decay model based on the experimental data for three CoPtCr-SiO2 PMR media with different thermal stability is obtained. Then, the performance of PR1ML channel for the 16/17(0,6/6) and 128/130(0,16/8) codes as a run-length-limited (RLL) code is evaluated by computer simulation using the model. Moreover, the relationships between the elapsed time and the BER are obtained for the combinations of two RLL codes and three PMR media and their performances are compared. The results show that for the combination of the 128/130(0,16/8) code and the medium with the poorest thermal stability, the degradation with the elapsed time is noticeable compared with the other combinations.

DOI： 10.1109/TMAG.2007.893422

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

An LDPC coding and iterative decoding system is studied in perpendicular magnetic recording (PMR) with a bit-patterned medium. We propose an iterative decoding scheme using attenuated extrinsic information from a sum-product decoder, and the bit error rate (BER) performance of the LDPC coding and iterative decoding system is evaluated by R/W computer simulations. It has been clarified that at an areal density of 1 Tbpsi the proposed system provides a jitter margin of the island edges of approximately 0.6% larger than the conventional system using (3, 18)-regular LDPC code.

DOI： 10.1109/TMAG.2007.893421

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

本論文では,バーストを伴う垂直磁気記録再生系において,LDPC符号化・繰返し復号化方式の性能評価を行っている.まず,バースト検出器を適用したLDPC符号化・繰返し復号化方式の記録再生系,バースト情報を用いた復号法及びバースト検出器について述べている.次いで,計算機シミュレーションにより所定のデータ内に誤りなしとなるための所要SN比とバースト長の関係を求め,バースト検出器を用いない従来方式と比較検討を行った.その結果,SNR=23dBにおいて,従来方式は約100チャネルビットのバースト耐性しかないのに対して,提案方式は約300チャネルビットのバースト耐性が得られることが明らかとなった.

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Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/INTMAG.2006.376512

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人日本磁気学会  

Read channels such as PRML systems are key technologies in HDD design, and are often evaluated by computer simulation using a read/write channel model as well as an actual R/W channel such as a spin-stand. In PRML read-channel simulations, signicant phenomena such as media noise, MR nonlinearity and thermal asperity should be taken into account, in order to make the simulation results similar to those obtained with a virtual drive. In this review, magnetic recording channel simulation is explained by adopting a perpendicular magnetic recording R/W channel model that takes account of the above phenomena.

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Language：Japanese   Publisher：The Magnetics Society of Japan  

It is known that jitter-like noise in perpendicular magnetic recording system is large compared with longitudinal magnetic recording system. In this paper, the recording density and the amount of magnetic transition-jitter from the signal processing point of view are assumed to be same in both recording systems, and the performance comparison of GPRML systems are performed. It is clarified that the perpendicular magnetic recording system shows the good BER performance compared with the longitudinal magnetic recording system, and it has large allowance of magnetic transition-jitter.

DOI： 10.3379/jmsjmag.29.432

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Other Link： http://dl.ndl.go.jp/info:ndljp/pid/10467017

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人日本磁気学会  

It is known that jitter-like noise in perpendicular magnetic recording system is large compared with longitudinal magnetic recording system. In this paper, the recording density and the amount of magnetic transition-jitter from the signal processing point of view are assumed to be same in both recording systems, and the performance comparison of GPRML systems are performed. It is clarified that the perpendicular magnetic recording system shows the good BER performance compared with the longitudinal magnetic recording system, and it has large allowance of magnetic transition-jitter.

DOI： 10.3379/jmsjmag.29.432

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

ジッタ性媒体雑音とMR非線形ひずみを伴う垂直磁気記録チャネルにおけるニューラルネットワーク等化の検討を行っている.まず, ハイブリッドGA (Genetic Algorithm)を用いたニューラルネットワーク等化器の簡単化を提案している.次いで, 簡単化されたニューラルネットワーク等化器を備えたPR2ML方式のビット誤り率特性を求め, 従来のニューラルネットワーク等化器及びトランスバーサルフィルタ等化器の場合と比較検討した.その結果, 従来のニューラルネットワーク等化器及びトランスバーサルフィルタ等化器の場合に対する簡単化されたニューラルネットワーク等化器を用いたPR2ML方式のSN比改善度は, それぞれ約0.8, 2.0dBとなることが明らかとなった.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

In this paper, post-processors for the partial-response maximum-likelihood (PRML) channel combined with the Reed-Solomon (RS) encoder/decoder are studied in perpendicular magnetic recording. The bit error rate (BER) performance is obtained by read/write experiments using a spin-stand with a perpendicular medium and single-pole-type/giant magnetoresistive (SPT/GMR) head. The experimental results show that post-processors improve linear densities of about 10-20 kBPI in perpendicular magnetic recording. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2004.10.067

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人日本磁気学会  

In a hard disk drive (HDD), a postprocessor is used for correcting the random error in a PRML (Partial Response Maximum Likelihood) channel. However, the postprocessor needs an error-detecting code, such as a single parity check code, and the code rate decreases. This paper proposes an erasure correction by Reed-Solomon (RS) code using Squaredv Distance-Increase (SDI) instead of a postprocessor. This system does not need any error detecting code. The performance is obtained by computer simulation and is compared with that of the error correction system using a postprocessor. The results show that the proposed system provides an SNR improvement of about 2.6dB compared with the system using a postprocessor in a perpendicular magnetic recording channel with random and burst errors.

DOI： 10.3379/jmsjmag.29.101

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

In this study, we investigate the influence of overwrite (O/W) noise on the performance of PRML channels in a perpendicular magnetic recording system in order to find the good PRML channels. The results show that the performance of PRML systems degrades if the SNR for overwrite noise is less than 35 dB and the noise-predictive PRML system is also effective for minimizing the influence of O/W noise on the performance. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2004.10.069

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE Computer Society  

DOI： 10.1109/intmag.2005.1463929

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

In this paper, the interactive processing between a partial-response maximum-likelihood (PRML) channel and a decoder for the Reed-Solomon (RS) code is studied in perpendicular magnetic recording channel. Whereas in conventional systems a run-length-limited (RLL) encoder/decoder is insides the RS encoder/decoder, in this paper, we permute their positions so that the PRML channel and RS decoder can interact. Accordingly, the RS decoder can acquire reliability information from a PRML, channel without interruption by the RLL decoder. It is demonstrated by computer simulation that the proposed system proAdes an SNR improvement of 0.8-1.1 dB compared vvith a conventional system at a linear density normalized by user bit interval, K, of 1.5.

DOI： 10.1109/TMAG.2004.829284

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

ヘリカルスキャンアジマス記録では,隣接トラックからのクロストークが高密度記録を阻害する主因の一つとなっている.このクロストークは有色雑音であるので,従来のPRML(Partial Response Maximum Likelihood)方式の再生信号処理では十分な性能を得ることができなかった.本論文では,ヘリカルスキャンアジマス記録にNPML(Noise Predictive Maximum Likelihood)方式を適用した場合の性能検討を行った. NPML方式のビット誤り率とPRML方式のビット誤り率を計算機シミュレーションにより求め,比較検討した.その結果,ビット誤り率10^<-5>において,NPML方式によるSN比改善は約4.5dBとなった.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

近年,記録符号としていくつかの誤り訂正符号を連接符号として用いる様々な記録符号化・復号化方式が検討され,その効果的な特性改善が報告されている.そこで本論文では,ディジタル通信の分野においてその高い誤り訂正能力でよく知られている高次元パリティ検査符号と,パーシャルレスポンス等化される磁気記録チャネルの組合せを統一してとらえる連接符号化・復号化方式を提案する.また,高次元パリティ検査符号の復号法として,パリティ検査線ベクトルによる誤り検出(仮判定)と,各シンボルの信頼度に対するしきい値判定(本判定)とを組み合わせる軟判定復号法を新たな可変しきい値復号法の一つとして提案している.そして,本方式と従来の16/17(0,6/6)符号化・復号化方式との誤り率特性の比較検討を行い,本方式はビット誤り率10^<-4>で約3.0dB程度のSN比改善が得られることを明らかにしている.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人日本磁気学会  

The remarkable increase in the recording density of hard disk drives (HDDs) owes much to the improvement of signal-processing technologies. Current commercial HDDs use longitudinal recording, and the recording density is coming close to the superparamagnetic limit. Thus, perpendicular magnetic recording is being widely studied as a promising recording system for achieving high-density recording. To achieve this, however, requires the development of excellent signal-processing, as in the case of longitudinal recording systems. In this paper, we first explain PRML systems as fundamental signal-processing technologies for perpendicular magnetic recording. We then describe jitter-like medium noise (JLMN) and its influence on the performance of PRML systems from the signal-processing point of view, and show the effect of noise-predictive PRML systems on JLMN. We also introduce iterative decoding systems capable of improving the performance significantly.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCRIPTA TECHNICA-JOHN WILEY & SONS  

We studied an improvement in the error rate performance of the PRML system in perpendicular magnetic recording. We improved the decoder performance by adopting an AR channel model in the estimation calculation of the input sequence in Viterbi decoding. We determined the required signal-to-noise ratio at the readout point and the line recording density needed to achieve a bit error rate of 10(-4) from computer simulations and recording and playback tests using a spinstand, and compared them to a conventional PRML system. The results clearly showed improved performance in the PRML system by using a Viterbi decoder employing the AR channel model. (C) 2004 Wiley Periodicals, Inc.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

最近のハードディスク装置の記録密度の目覚ましい向上は信号処理技術の進展に負うところが大である将来の超高密度記録のための記録方式として垂直磁気記録方式が期待されており,そのための優れた信号処理方式の開発が望まれる。本稿では,まず,垂直磁気記録のための信号処理方式の基礎となるPRML方式について解説する。次いで,垂直磁気記録において支配的な雑音であるジッタ性媒体雑音に有効なARチャネルモテルを用いたPRML方式について述べる。更に,大幅な性能改善が期待できる繰返し符号・復号化についても紹介する

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Turbo decoding with an embedded autoregressive (AR) channel model is studied in an actual perpendicular magnetic recording channel. Performance of the a posteriori probability (APP) decoder is improved by applying an, AR channel model in order to estimate the decoder input sequence. The bit-error-rate (BER) performance,is obtained by read/write experiments using a spin stand with a perpendicular medium and an single-pole-type/giant magnetoresistive (SPT/GMR) head. The results show that our turbo coding and iterative decoding system using an AR channel model improves the BER performance.

DOI： 10.1109/TMAG.2003.816482

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

ハードディスク装置で用いる信号処理方式の一つとして, PRML(Partial Response Maximum Likelihood)方式がある.近年の大容量化に対する要請にこたえるために,このPRML方式に用いられる記録符号として,従来以上に高能率で符号系列間に強い制約をもつものの開発が強く求められている.そこで,本論文では,従来よく用いられている16/17(0,6/6)符号に比べて,更に高能率なラン長制約符号を提案する.そして,新たに構成するラン長制約符号の符号化・復号化則と誤り伝搬に関する性能評価を示し,従来の16/17(0,6/6)符号よりも優れた性能をもつことを明らかにする.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

ジッタ性媒体雑音を伴う垂直磁気記録再生チャネルにおけるNPML(Noise Predictive Maximum Likelihood)方式の性能評価を行っている.PR1チャネルに対するPRML方式とNPML方式のビット誤り率を計算機シミュレーションにより求め,比較検討を行った.その結果,規格化線密度が1.5におけるPRML方式に対するNPML方式のSN比改善度は,最大で約15.8dBとなることが明らかとなった.また10^<-4>のビット誤り率を達成するのに要する読出し点の所要SN比と規格化線密度の関係を求めた.その結果,全雑音電力に対するジッタ性媒体雑音電力の割合が小で規格化線密度が大となるほど,NPML方式によるSN比改善量は大となることが明らかとなった.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

垂直磁気記録におけるPRML方式の誤り率特性改善について検討している.ビタピ復号における入力系列の推定値演算にARチャネルモデルを適用することにより,復号器の性能向上を図っている.そこで,計算器シミュレーション,スピンスタンドを用いた記録再生実験により10_<-4>のビット誤り率を達成するのに要する読出し点の所要SN比,線記録密度を求め,従来のPRML方式との比較検討を行っている.その結果,ARチャネルモデルを適用したビタビ復号器によりPRML方式の性能改善が得られることを明らかにしている.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Inst. of Image Information and Television Engineers  

The distortion due to low frequency cutoff degrades the performance of partial response maximum likelihood(PRML) system in a perpendicular magnetic recording. This paper presents an application of guided scrambling(GS) code to PRML system as an effective strategy for avoiding the distortion. The bit error rate performances of PR2ML systems for two types of GS codes, Galois field (GF) additive type and convolutional operation type, are obtained. The results indicate that GS coded PR2ML systems can achieve gains of about 6.3dB for GF additive type code and 4.4 dB for convolutional operation type code over conventional Reed-Solomon coded PR2ML system at a normalized linear density of 1.5, a power ratio of jitter-like media noise to total noise of 80% and a low-cutoff frequency normalized by bit rate of 0.002.

DOI： 10.3169/itej.57.1520

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

In this paper, we reports that the application of an appropriate NPML (Noise-Predictive Maximum Likelihood) system to the read channel can effectively improve the error rate performance.

DOI： 10.1109/INTMAG.2003.1230528

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

In this paper, we propose a new post-processing for PRML-AR system, and experimentally show that our proposed system shows a good BER performance in the perpendicular magnetic recording channel. RLL codes and 4-interleaved parity check codes are analyzed in this study.

DOI： 10.1109/INTMAG.2003.1230525

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

In this paper proposed the posteriori probability (APP) decoder which obtains the estimated values for the respective state transitions by using an autoregressive (AR) channel model. This paper also explained the BER performance in the perpendicular magnetic recording channel.

DOI： 10.1109/INTMAG.2003.1230520

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Performance improvement of partial-response maximum-likelihood (PRML) system in the perpendicular magnetic recording channel with jitter-like noise is studied. Performance of a Viterbi detector is improved by applying an autoregressive (AR) model in order to estimate the detector input sequence. The required signal-to-noise ratio to achieve a bit-error rate (BER) of 10 is obtained by computer simulation. In addition, a BER performance is also obtained by read/write experiments using a spin-stand. The results show that the proposed PRML system using an AR model exhibits better performance when compared with the normal PRML systems without an AR model.

DOI： 10.1109/TMAG.2002.801902

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

Recently, the encoding/decoding systems based on concatenated codes with several error correction codes are actively studied and effective performance improvements are obtained. In this report, the system for recoding code is proposed using a high dimensional parity check code known as a concatenated code with high error correction capability in digital communication. Especially, our soft decision decoding method is based on error detection using a parity check (tentative decision) and threshold decision for the reliability of error symbols (final decision). As a result, it is clear that the performances of these parity check codes are superior to that of the conventional 16/17(0,6/6) code.

DOI： 10.11485/itetr.26.37.0_1

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

The performance of guided scrambling (GS) coded PRML system in a perpendicular magnetic recording channel with jitter-like media noise and distortion due to low frequency cutoff is studied. The bit error rate performance of PR2ML systems for two types of GS codes, Galois field (GF) additive type and convolutional operation type, is obtained and compared with that of conventional Reed-Solomon (RS) coded PR2ML system. The results show that the SNR improvements of GS coded PR2ML systems over RS coded PR2ML system are about 9.3 dB for GF additive type code and 8.3 dB for convolutional operation type code at a normalized linear density of 1.5, a power ratio of jitter-like media noise of 80% and a low-cutoff frequency normalized by bit rate of 0.003.

DOI： 10.11485/itetr.26.37.0_13

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

情報ストレージ装置の高信頼性と大容量化を図るために,高密度ディジタル磁気記録に適した信号処理技術の開発が求められている.16/17MTR符号と巡回冗長検査符号を組み合わせた連接符号化方式は,軟出力ビタビアルゴリズムによる最ゆう復号と誤りパターンとのゆう度差から得られる信頼度情報を用いた消失誤り訂正を行うリスト復号を組み合わせた優れた方式として知られている.本論文では,新たに上記の連接符号化方式に軟出力双方向ビタビアルゴリズムに基づく最ゆう復号と双方向ビタビ復号の軟出力から得られる信頼度情報によって誤り訂正を行うリスト復号を用いる.そして,各種PRML方式を組み合わせた場合のビット誤り率特性を計算機シミュレーションにより求め,特性の良いPRML方式を明らかにした.

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

BER performance improvement of PRML system in perpendicular magnetic recording is studied. The performance of Viterbi detector is improved by applying an AR model to the estimation of input sequence. The required SNR's to achieve a BER of 10^<-6> are obtained by computer simulation and they are compared with those of conventional system. The results show that PRML system with Viterbi detector using an AR channel model provides a good performance.

DOI： 10.11485/itetr.26.1.0_25

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCRIPTA TECHNICA-JOHN WILEY & SONS  

The performance of a partial response maximum likelihood (PRML) system in perpendicular magnetic recording that uses double-layered media perpendicular to the MR head is evaluated. The codes of (1,7) RLL and 16/17 (0,6/6), which are commonly used in modern hard disk equipment, are used as the recording codes. The relationship between the normalized linear density and the desired 4 SNR at the reading point for a bit error rate of 10(-4) is determined from a computer simulation, assuming equalization by a transversal filter, and a comparative study is performed. It is shown that a (1,7) RLL coded PRML system has better performance when the recording density is comparatively low. For high recording density, a 16/17 (0,6/6) coded PRML system has shown better performance. (C) 2002 Wiley Periodicals, Inc.

DOI： 10.1002/ecjb.1106

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

In this work, the coded partial response (PR) system based on serially concatenated error control codes is described. The component codes of the concatenated codes are a low density parity check (LDPC) code and a punctured convolutional (PC) code. In our system, the LDPC code is used as an inner code and is an important random code which can approach Shannon's capacity limit. A practical decoding method of the LDPC code is known as the sum-product decoding algorithm or belief propagation. Furthermore, the PC code is used for an outer code and can enhance the minimum squared Euclidean distance for the coded PR system. The sequence of the PC code has a single parity check capability for the concatenated coding.

DOI： 10.1109/INTMAG.2002.1000870

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

The performance of noise predictive maximum likelihood(NPML) system in helical scanning azimuth recording with crosstalk noise is studied. The bit error rate of PR1NPML system is obtained by computer simulation and comnared with that of PR1ML system. The results show that the SNR improvements of PR1NPML system over PR1ML system at a bit error rate of 10^<-5> and a normalized linear density of 2.5 are about 0.3 and 4.5 dB for the cases without crosstalk noise and with crosstalk noise, respectively, and the degradation of the bit error rate performance due to the crosstalk noise has been effectively reduced.

DOI： 10.11485/itetr.26.80.0_19

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

The neural network equalization in perpendicular magnetic recording channel with jitter-like media noise and MR nonlinear distortion is studied. A method of simplification of neural network using a hybrid genetic algorithm (GA) is proposed. Then, the bit error rate performance for PR2ML system with a simplified neural network equalizer is obtained and compare with those of conventional neural network and transversal filter equalizers. The results show that the SNR improvements of PR2ML system with simplified neural network equalizer over PR2ML system with conventional neural network equalizer and transversal filter equalizer are about 1.0 and 1.5dB, respectively.

DOI： 10.11485/itetr.26.65.0_1

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

The effective signal processing system for jitter-like medium noise is required in a perpendicular magnetic recording. In this paper, a post-processor is studied for PRML system using AR (Autoregressive) channel model which has a good performance in the perpendicular magnetic recording system where jitter-like medium noise is dominant. An interleaved parity check coding to search an error event and the method to identify the position of the error are proposed. Furthermore, the performance is evaluated in a real channel on a spinstand with a read/write head, which consist of a single pole type head and a GMR head, and a perpendicular recording medium. The results show that the linear density of our system improves about 16% (100kBPI) compared with that of the conventional PR1ML system.

DOI： 10.11485/itetr.26.65.0_7

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

The performance of noise predictive maximum likelihood(NPML)system in a perpendicular magnetic recording channel with jitter-like media noise is studied. The bit error rates of NPML systems for the PR2, E^2PR3 and E^2PR4 channels are obtained by computer simulation and theoretical method. The relationship between the ratio R_J of the jitter-like media noise power to the total noise power at the reading point and the required SNR to achieve a bit error rate of 10^<-4> is also obtained and compared with that of the conventional PRML system. The results show that the SNR improvements of NPML systems over PRML systems are about 2.1, 2.8 and 5.6 dB for the PR2, E^2PR3 and E^2PR4 channels, respectively, at a normalized linear density of 1.5 and R_J=50%.

DOI： 10.11485/itetr.25.82.0_1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

Turbo coding is widely known as one of effective error control coding techniques in various digital communication systems since this coding method has proposed by C. Berrou, etc in 1993. In digital magnetic recording, it has been cleared that the error correcting capability of turbo coding is superior to most of conventional recording codes as a matter of course. But, the performance of a partial response maximum-likelihood (PRML) system combined with any recording code is degraded by many undesirable factors or effects. To improve the performance of the PRML system in high areal density recording, it is useful to adopt a higher order PRML system or high rate code in a general case. In this paper, the rate 32/34 turbo code combined with an enhanced extended class-4 partial response (E(2)PR4) is proposed. We call this trellis coded partial response (TCPR) system the rate 32/34 turbo-coded E(2)PR4 (32/34 TC-E(2)PR4). Our proposed TCPR system can be expected to get large coding gain and improve the performance of PRML system. As a result, the proposed coding system provides a good performance compared with the conventional systems. In especial, our system can achieve a BER of 10(-5) with SNR of approximately 1.5 dB less than the conventional 8/9 maximum transition run (MTR) coded E(2)PR4ML system at a normalized linear density of 3.

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

Performance improvement of an APP decoder in a serially concatenated turbo coding and decoding system is studied in perpendicular magnetic recording. An estimator of output levels from a PR channel in APP decoder is improved, and BER performance is obtained by computer simulation. The results show that the performance is improved. It is also clarified that the performance improvement is obtained by extension of coding and decoding block size.

DOI： 10.11485/itetr.25.63.0_21

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

A modeling for PR channel in a perpendicular magnetic recording using AR model is studied. The AR model is constructed from the actual channel outputs obtained by a read/write experiment using a spinstand. The signal and noise spectra, the distributions of signal level, the error rate performances, and the error patterns for PR channel model are obtained. The results show that the characteristics agree well with those of the actual channel. It is also shown that a model of read/write channel is obtained by adding the reverse characteristic of equalizer to PR channel model.

DOI： 10.11485/itetr.25.63.0_15

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Performance of a timing recovery system for perpendicular magnetic recording channels is studied. The system detects timing error from pre-equalized waveform of a basic PR system such as PR1, and corrects the timing of sampled sequence using an interpolated filter. The results show that the system which uses PR1 system as the pre-equalization and directly compensates the reproduced waveform exhibits good performance. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0304-8853(01)00410-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The error events for PR2ML system in perpendicular magnetic recording using double-layered medium with additive white Gaussian noise, jitter-like noise and distortion due to low frequency cut-off are studied. The result shows that the error event "+ - +00" extremely increases as the cut-off frequency becomes high. The error events obtained by computer simulation are also compared with those obtained by the R/W experiments. It is clarified that the simulated error events approximately correspond to the experimental results. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0304-8853(01)00411-5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The performance of PRML systems in a perpendicular magnetic recording channel using a double-layered medium is evaluated. The required SNR to achieve a BER of 10(-4) is obtained by computer simulation. PRML systems hich provide good performance in the perpendicular magnetic recording channel with the various power ratios of jitter-like noise to white noise are shown. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0304-8853(01)00356-0

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We evaluate the BER performance of various MTR coded PRML systems characterized by the polynomials with only positive coefficients in a perpendicular magnetic recording channel using a double-layered medium with jitter-like noise by computer simulation. The results show that 3/4 MTR coded PRML systems exhibit good performances compared with 16/17 MTR coded PRML systems. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0304-8853(01)00409-7

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

A parallel concatenated parity check coding system, the decoding complexity of which is smaller than that of the conventional turbo coding system with the recursive systematic convolutional(RSC) codes, is proposed and the performance is evaluated. First, a construction method of encoding and decoding is shown. Then, the required SNR's to achieve a BER of 10^<-4> for the combinations of the coding rates 16/18 and 32/34 parallel concatenated codes and the parity check coded E^2PR4 systems are obtained by computer simulation. Lastly, their performances are compared with that of the conventional 16/17(0, 6/6) coded E^2PR4ML system. It is shown that the proposed system provides the better performance than the conventional system.

DOI： 10.11485/itetr.25.37.0_25

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

In this paper, a rate 19/20 trellis code matched to the partial response (PR) channel is presented, Our trellis code is designed on a multidimensional Euclidean space for which the minimum free Euclidean distance is Larger than conventional recording codes. By using this trellis coding, a trellis coded partial response (TCPR) system is defined for the enhanced extended class-4 partial response (E-2 PR4) channel. Further, the decoding method for this TCPR system is based on the syndrome-former trellis decoding. The number of add-compare-selects (ACS's) in our system is fewer than that of conventional Viterbi decoding. The result shows that TCPR system employing this rate 19/20 trellis code with the constraint length 7 for the E-2 PR4 has an excellent performance compared with the conventional 8/9 maximum transition run (MTR) coding system in high-density recording.

DOI： 10.1109/20.917614

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

The BER performance of iterative decoding systems and PRML systems in a perpendicular magnetic recording channel is experimentally investigated. A performance evaluation system consisting of a spinstand, a recording waveform generator, a digital storage oscilloscope and a personal computer was used, PR1ML, PR2ML, EPR3ML, E(2)PR3ML and ME(2)PR4ML systems are discussed as a PRML channel. The 8/9 and 16/17 iterative-decoding systems consists of the encoder, with RSC encoder serially concatenated with preceded PR channels and the iterative decoder with APP modules using Max-log-MAP algorithm.
The results show that EPR3ML and E(2)PR3ML provide good BER performance in a perpendicular magnetic recording channel and that the iterative decoding system is also an efficient way to improve the BER performance in the channel.

DOI： 10.1109/20.917602

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

In this report, improvement of high rate(0, G/I)codes and it's performance evaluation are studied. Our new construction method of(0, G/I)code is based on a minimized G constraint. New 32/33(0, 6)and 64/65(0, 8)codes are obtained by using this method. As a result, computer simulation shows that both of these(0, G/∞)codes with E^2PR4ML systems provide the better performance than the conventional 16/17(0, 6/6)code.

DOI： 10.11485/itetr.25.1.0_25

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

The 3/4MTR coded PRML system for perpendicular magnetic recording using double layered medium is studied. The BER performance is obtained by the experiments using a spin-stand system, and it is compared with that of 16/17 MTR coded PRML system. The results show that the 3/4MTR coded PRML system exhibits a good performance.

DOI： 10.11485/iteac.2001.0_35

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Inst. of Image Information and Television Engineers  

The performance of serially concatenated turbo coding systems using various RLL codes was evaluated and compared with that of PRML systems in a perpendicular magnetic recording channel. The error rates of these systems were experimentally estimated by an actual R/W channel using a spinstand with a double-layered perpendicular magnestic recording medium. The experimental results show that among the PRML systems, PR1ML, PR2ML, and E2PR3ML had good performance. We also found that our turbo coding system using a PR2 system had the best performance among all RLL-coded serially concatenated turbo coding systems we investigated. A 64/65(0,8) code was found suitable for our turbo coding system.

DOI： 10.3169/itej.55.1353

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCRIPTA TECHNICA-JOHN WILEY & SONS  

Trellis codes are a form of recording codes considered to have good compatibility with PRML systems, which are signal-processing systems that are effective for digital magnetic recording. In this paper, trellis codes which are compatible with PR4 and EPR4 are constructed by a set partitioning method. The best trellis codes are constructed by defining a signal constellation on the basis of output symbols allowing a partial response scheme and by partially dividing sets on a multidimensional Euclidean space. It is shown that trellis codes having a coding rate of 9/10 and bundle lengths of 6 and 7 can be obtained for PR4 and EPR4 systems using Nyquist equalization, and that the SN ratios are improved by 2.4 and 2.3 dB for the existing 8/9 (0,4/4) codes for the PR4 system and 16/17 (0,6/6) codes for the EPR4 system at a bit error rate of 10(-4). (C) 2001 Scripta Technica, Electron Comm.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

The infuluence of jitter-like noise on the performance of PRML systems in the perpendicular magnetic recording channel using a double layered medium is studied, Both the bit error rate (BER) performance and the required SNR to achieve a BER of 10(-6) are obtained by computer simulation and exhibit good performance even for the channel in which the power ratio of jitter-like noise to white noise is fifty-fifty.

DOI： 10.1109/20.908343

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

The bit-error rate (BER) performance of perpendicular magnetic recording using a single-layered medium is studied, 16/17 (0, 6/6) code is adopted as a recording rode, and is combined with various PRML systems to achieve higher linear recording density. The results of read/write experiments using a spinstand system show that the higher-order PRML systems such as E-2 PR4ML and E-3 PR4ML systems exhibit good BER performance in our investigated PRML systems.

DOI： 10.1109/20.908341

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

Various PRML systems combined with 3/4 MTR code in the perpendicular magnetic recording using a double-layered medium are studied. The relationship between the required SNR to achieve a bit error rate of 10^<-4> and the normalized linear density is obtained by computer simulation and it is compared with that for 16/17(0, 6/6)code or(1, 7)RLL code. The results show that PRML sysytems combined with 3/4MTR code exhibit good performance.

DOI： 10.11485/itetr.24.33.0_1

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

Performance of iterative decoding for various ME^2PR4 channels serially concatenated with code rate 8/9 or 16/17 RSC code is evaluated. The required SNR to achieve a bit error rate of 10^<-4> is obtained by computer simulation and it is compared with that of the conventional 16/17(0, 6/6)coded E^2PR4ML system. The results show that the proposed systems of coding rate 8/9 and 16/17 exhibit excellent performance compared with the conventional system. The proposed system with code rate 8/9 has good performance in comparatively low recording densities, while the system with coding rate 16/17 shows good performance in high densities.

DOI： 10.11485/itetr.24.33.0_7

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

Construction method and performance evaluation of high rate(0, G/I)codes are studied. First, construction method of a 32/33(0, 10/10)code is described and an extended 64/65(0, 20)code is designed by using this 32/33(0, 10/10)code. Then, the bit error rate(BER) performance of these coded EPR4ML, E^2PR4ML and ME^2PR4ML systems and the required SNR to achive a BER of 10^<-4> are obtained by computer simulation and compared to those for the conventional 16/17(0, 6/6)code. The results show that both of the 32/33(0, 10/10)code and 64/65(0, 20)code provide the better performance than the 16/17(0, 6/6)code.

DOI： 10.11485/itetr.24.33.0_13

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人日本磁気学会  

The bit-error rate (BER) performance of 16/17 (0, 6/6) coded PRML systems for a single-layered perpendicular medium was studied by conducting read/write experiments using a spinstand system. The results show that the E^3PR4ML system exhibits the best performance among the PRML systems evaluated in this paper, and achieves a BER of less than 10^&lt;-6&gt; at a high linear density such as 375 kbpi.

DOI： 10.3379/jmsjmag.24.235

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

パーシャルイレージャを伴う記録・再生系へのニューラルネットワークFDTS / DF方式の適用について検討を行っている.まず, パーシャルイレージャを伴う記録・再生チャネルのモデル及びニューラルネットワークFDTS / DF方式について述べている.次いで, 計算機シミュレーションによりビット誤り率を求め, 従来のFDTS / DF方式の場合との性能比較を行った.その結果, ニューラルネットワークFDTS / DF方式の場合の誤り率特性が従来のFDTS / DF方式の場合よりも良好となり, 10^&lt;-4&gt;の誤り率において約2.9dBのSN比改善が得られることを明らかにしている.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

MRヘッドと垂直2層膜媒体を用いた垂直磁気記録のためのPRML(Partial Response Maximum Likelihood)方式の性能評価を行っている.最近のハードディスク装置によく用いられている(1, 7)RLL符号と16 / 17(0, 6 / 6)符号を記録符号とし, トランスバーサルフィルタによる等化を仮定して計算機シミュレーションにより規格化線密度とビット誤り率10^&lt;-4&gt;を達成するのに要する読出し点の所要SN比の関係を求め, 比較検討した.その結果, 比較的低密度記録においては(1, 7)RLL符号化PRML方式が, 高密度記録においては16 / 17(0, 6 / 6)符号化PRML方式が良好な特性を示すことが明らかとなった.

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

This report proposes a new 8/9 MTR code which is a type of systematic form. The problem of an error propagation in decoding is evaded by using this coding method. It is shown that the proposed systematic coding can provide a performance inprovement over the conventinal non systematic one.

DOI： 10.11485/iteac.2000.0_100

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

The iterative decoding system for perpendicular magnetic recording using double layered medium is sutdied. The BER perfoemance of our system is obtained by the experiments using a spin-stand system, and it is compared with that 16/17 (0,6/6) coded E^2PR4ML system. The results show that our proposed system exhibit an excellent performance.

DOI： 10.11485/iteac.2000.0_92

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

Error patterns of 16/17(0,6/6) coded PR(1,2,2,1)ML system fpr perpendicular magnetic recording using double layred medium are studied. The error pattern which affects the performance in the PRML system in clarified by investigating the dominant error patterns in the PRML system.

DOI： 10.11485/iteac.2000.0_98

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCRIPTA TECHNICA-JOHN WILEY & SONS  

Performance is compared for various PRML systems for three types of codes, (1,7)RLL code, 8/9(0,4/4) code, and 16/17(0,6/6) code. In the high-density digital magnetic recording system with partial erasure, the bit error rate is derived by computer simulation for PR4ML, EPR4ML, E(2)PR4ML, ME(2)PR4ML, PR(1,1,1,-1,-1,-1)ML, PR(1,2, 1,-1,-2,-1)ML, and PR(1,2, 1,0,-1,-2,-1)ML systems. It is found that good performance is exhibited by the PR(1,2,1,-1,-2,-1)ML system for the (1,7)RLL code, and by the PR(1,2,1,0,-1,-2,-1)ML system for the 8/9(0,4/4) and 16/17(0,6/6) codes. (C) 1999 Scripta Technica.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

In various digital wireless communication systems, it is known that turbo coding provides an error rate performance within a few tenths of a dB of the theoretical Shannon limit. The error correcting capability of turbo coding is attractive for a recording code in a digital magnetic recording system. The performance of a partial response maximum-likelihood (PRML) system with any recording code is degraded by many undesirable factors such as linear and nonlinear distortions. For improving the performance of the PRML system, it is useful to adopt a high-order PRML system or high rate code in general. In this paper, the two-track recording system using turbo coding which can increase the coding rate over 1 and improve the performance is proposed. Turbo-coding provides a near-ML performance by the suboptimum symbol-by-symbol maximum a posteriori probability (MAP) decoding algorithm. Our proposed turbo-coded class 4 partial response (PR4) systems use the rate 4/6, 8/10 and 16/18 turbo codes for high-density two;track-digital magnetic recording. The error rate performance is obtained by computer simulation, taking account of the partial erasure which is a prominent nonlinear distortion in high-density recording. As a result, the proposed systems are hardly affected by partial erasure and maintains good performance compared with the convectional NRZ coded PR4ML system.

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Language：English   Publishing type：Research paper (scientific journal)  

Recently, it is widely known that the partial response maximum-likelihood (PRML) system has attracted much attention as one of indispensable signal processing technique for achieving high density digital magnetic recording. But, the performance of PRML system is degraded by many undesirable causes in recording channel. For improving the performance, it is desirable to use any high order PRML system or high rate code. Our proposed two-track recording method increases the coding rate over 1, and contributes to decrease these degradation effects. The recording code in our system adopts a turbo code which provides a substantial near-ML performance by the suboptimum iterative decoding algorithm. In this paper, the turbo coded class four partial response (PR4) systems using the rate 4/6, 8/10 and 16/18 codes for high density two track digital magnetic recording are proposed. The error rate performance of the proposed system is obtained by computer simulation taking account of the partial erasure, which is one of nonlinear distortions at high densities. The performance of our system is compared with that of the conventional NRZ coded PR4ML system. The result shows that the proposed system is hardly affected by partial erasure and keeps good performance in high density recording. In especial, the proposed system using the rate 16/18 turbo code can achieve a bit error rate of 10-4 with SNR of approximately 12.2 dB less than the conventional NRZ coded PR4ML systems at a normalized linear density of 3.

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

8/9 GMTR code is constructed and its bit error rate(BER)performance is evaluated. We assumed three types of read/write channels using a longitudinal medium, a single layered perpendicular medium and a double layered perpendicular medium. BER performance is obtained by computer simulation, and compared with those of 16/17(0.6/6)code and 16/17 MTR code. The results show that the proposed 8/9 GMTR coded E^3PR4ML system exhibits the excellent performance in all channels assumed here.

DOI： 10.11485/itetr.23.77.0_1

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

An application of the neural network equalization to the PRML channel with jitter-like media noise is studied. First, a model of the read/write channel with jitter-like media noise and a neural network equalizer are described. Then, the bit-error rate of the 16/17(0, 6/6)coded EPR4ML and E^2PR4ML systems using a neural network equalizer is evaluated by computer simulation and the performance is compared with that of the conventional systems using a transversal filter. The results show that the neural network equalization can reduce the influenece of jiter-like media noise on the performance.

DOI： 10.11485/itetr.23.77.0_29

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

As a PRML system for perpendicular magnetic recording using a double-layered medium and an MR head, a new PR(1, 2, 3, 3, 2, 1)ML system is proposed. The relationship between the required SNR to achieve a bit error rate of 10^-4 and a normalized linear density for(1, 7)RLL and 16/17(0, 6/6)recording codes is obtained by computer simulation and it is compared with those of conventional PRML systems. The results show that among these PRML systems the conventional(1, 7)RLL coded PR(1, 2, 3, 2, 1)ML systems shows the best performance in relatively low density recording while the(1, 7)RLL coded PR(1, 2, 3, 3, 2, 1)ML system has the best performance in high density recoding.

DOI： 10.11485/itetr.23.38.0_7

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

Recently, turbo coding is known as an effective one of error control coding in various digital communication systems. In this report, the system of the turbo coding and PRML is studied by using two-track recording method. The bit-error rate performances of coding rtate 4/6, 8/10 and 16/18 turbo coded PR4ML systems are obtained by computer simulation in high density read/write magnetic recording system with partial erasure. As a result, it is shown that the coding rate 16/18 turbo coded system can provide an improvement of about 12.6dB over the conventional NRZ-coded system at a bit error rate of 10^-4 and a normalized linear density of 3.

DOI： 10.11485/itetr.23.38.0_23

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

Bit error rate performance of PRML systems for the perpendicular magnetic recording using single-layer medium is studied. Error rates of both(1, 7)RLL coded PRML systems and 16/17(0, 6/6)coded PRML systems are estimated by recording and reproducing experiments using a spinstand with a single-layered medium and compared with those of a longitudinal medium. The results show that 16/17(0, 6/6)coded E^2PR4ML system in perpendicular magnetic recording using the single-layered medium has a excellent performance among those systems.

DOI： 10.11485/itetr.23.38.0_15

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCRIPTA TECHNICA-JOHN WILEY & SONS  

Recently, the demand for higher density digital recording has been increasing steadily. In this article, focusing on digital magnetic recording devices, such as magnetic disks and digital VTRs, a signal processing technique for achieving higher densities is described. First, the partial response system, Viterbi decoding method, and partial response maximum likelihood (PRML) system are described in detail. Next, various signal processing methods extensively studied in recent years for longitudinal magnetic recording are described. Recent research trends in signal processing methods responsive to nonlinear distortions, with allowance for nonlinear distortions, such as partial erasure as factors promoting error rate degradation in high-density recording, are discussed. The performances of various methods are compared. A signal processing method for vertical magnetic recording expected to be a promising technique for future high density recording is described. (C) 1999 Scripta Technica, Electron Comm Jpn Pt 2, 82(6): 25-45, 1999.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

本論文では, 従来知られる8/10MSN符号よりも, 更に高符号化率な9/10MSN符号を新たに構成する. そして, 高密度記録において, 磁気記録再生系に大きな影響を及ぼす非線形ひずみの一種であるパーシャルイレージャを考慮したビット誤り率を計算機シミュレーションにより求め, 性能評価を行う. ここで提案する9/10MSN符号は, ルックアップテーブルのみを用いて復号できる符号語のみを集合とし, 従来の8/10MSN符号と異なって, スライディングブロック復号器を必要としない構成としている. その結果, 規格化線密度3, ビット誤り率10^&lt;-4&gt;において, 提案した9/10MSN符号は, 従来の8/10MSN符号に比べて, 更に約2.3dBのSN比改善が得られることを明らかにしている.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

ディジタル磁気記録における有力な信号処理方式に挙げられるPRML方式に対する整合性の良い記録符号の一つとして, トレリス符号が考えられている. 本論文では, 集合分割法をもとにPR4, EPR4方式に整合するトレリス符号を構成する. 符号構成では, パーシャルレスポンス方式の許容する出力シンボルをもとに信号配置を定義し, 多次元ユークリッド空間上で部分集合分割し, 最良なトレリス符号を構成する. この結果, ナイキスト等化を用いたPR4及びEPR4方式に対して, 拘束長6, 7をもつ符号化率9/10トレリス符号を示し, 従来のPR4方式に対する8/9(0, 4/4)符号やEPR4方式に対する16/17(0, 6/6)符号に対し, ビット誤り率10^&lt;-4&gt;において, それぞれ2.4, 2.3dBのSN比改善が得られることを明らかにした.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCRIPTA TECHNICA-JOHN WILEY & SONS  

Partial response signaling with maximum likelihood detection (PRML) systems using a rate 11/12 punctured convolution code (PCC) as a recording code in digital magnetic recording are proposed. The bit error rate (BER) performance for several PRML systems for the rate 11/12PCC is obtained by computer simulation and compared with that for the conventional rate 8/9 code. It is shown that among these PRML systems, E(2)PR4ML systems for the rate 11/12PCC outperform those for the rate 8/9 code and provide an SNR advantage of about 3.4 dB at a BER of 10(-4) and a normalized linear density of 3. (C) 1999 Scripta Technica, Electron Comm Jpn Pt 2, 82(5): 54-62, 1999.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Various PRML systems for the (1,7) code and the 16/17 GCR code are experimentally studied. We constructed an experimental evaluation system for PRML channel using a spinstand and estimated the performance of various PRML systems. The results show that PR(1,1,1, -1, -1, -1)Ml, PR(1,2,1, -1, -1, -1)Ml and Pr(1,2,1,0, -1, -2, -1)ML for the (1,7) code have an excellent performance at high linear density recording. (C) 1999 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0304-8853(98)00867-1

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人日本磁気学会  

PRML systems for perpendicular magnetic recording using a single-layer medium were studied. Reproduced waveforms at linear densities of 150 to 300 kBPI were acquired by recording and reading-back experiments using a perpendicular single-layer medium, and dibit responses ware derived from these waveforms. Using these responses were derived from these waveforms. Using these responses in computer simulation, the performance of PRML systems for (1,7) RLL code was estimated from the SNR required at the reading point to achieve a bit-error rate of 10^&lt;-4&gt;. The results show that a PR (1,2,1,0,-1,-2,-1) ML system has a mech better performance than a PR5ML system at linear densities of 250 to 300 kBPI.

DOI： 10.3379/jmsjmag.23.1069

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCRIPTA TECHNICA-JOHN WILEY & SONS  

A conventional 8/10 MSN code was constructed so as not to generate a quasi-catastrophic sequence in the decoder trellis diagram, and needing sliding block decoders. In this article, a new 8/10 MSN code is designed by using a periodically time-varying trellis diagram. The proposed code has an improved squared Euclidean distance distribution between PR output sequences and an improved number of paired codewords that have minimum squared free Euclidean distance decreases as compared with the conventional code. Further, this code can be decoded simply by referring codeword sequences corresponding to data sequences in a look-up table, needing no sliding block decoder. As a result, the proposed 8/10 MSN-coded PR4ML system can provide about 0.8 dB SNR gain over the conventional system at a bit error rate of 10(-4) and a normalized linear density of 3. (C) 1999 Scripta Technica.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本磁気学会  

&amp;nbsp;&amp;nbsp;The partial response maximum likelihood (PRML) systems characterized by the higher order polynomials for perpendicular magnetic recording using a double-layered medium are studied. The relationship between the required SNR to achieve a bit erorr rate of 10&lt;sup&gt;-4&lt;/sup&gt; and a normalized linear density for (1,7)RLL and 16/17(0,6/6) coded PRML systems is obtained by computer simulation and compared with that of the conventional 16/17(0.6/6) coded EPR4ML system. The results show that among PRML systems discussed in this study the (1,7)RLL coded PR(1,2,3,3,2,1) ML,PR(1,2,1,0,-1,-2,-1)ML and PR(1,1,1,0,-1,-1,-1)ML systems and the 16/17(0,6/6) coded PR(1,2,3,3,2,1)ML,PR(1,3,4,4,3,1)ML and PR(1,2,1,0,-1,-2,-1)ML systems provide excellent performance and are superior to that of the 16/17(0.6/6) coded EPR4 ML system.

DOI： 10.3379/jmsjmag.23.1069

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Inst. of Image Information and Television Engineers  

A neural network canceller has been applied to the PR4ML channel with partial erasure. First, a model of the read/write channel with partial erasure and the neural network canceller are described. Then, the bit-error rate of the PR4ML channel is evaluated by computer simulation and the performance is compared with that of a conventional neural network equalizer and a Nyquist equalizer. The results show that the neural network canceller exhibits better performance than the conventional neural network equalizer and Nyquist equalizer.

DOI： 10.3169/itej.53.1615

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本磁気学会  

&amp;nbsp;&amp;nbsp;As efficient recording codes for an extend class-4 partial response (E&lt;sup&gt;2&lt;/sup&gt;PR4) system, the high rate punctured convolutional codes are proposed. These coding methods are based on deleting several symbols from an original low rate code. Therefore, these codes are decoded easy maximum likelihood (ML) algorithm for the original code. As a result, it is shown that the rate 32/33 punctured convolutional codes E&lt;sup&gt;2&lt;/sup&gt; PR4ML have about 1.0 and 2.6 dB advantage over the conventional rate 8/9 maximum transition run and 16/17 (0,6/6) coded systems at a bit error rate of 10&lt;sup&gt;-4&lt;/sup&gt;. Furthermore, by using soft-output Viterbi decoding, the error rate performance of a punctured system is improved over the conventional Viterbi decoding method.

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

The PRML system for perpendicular magnetic recording using a double-layered medium and an MR head are studied. The required SNR of (1,7)RLL coded PR(1,2,3,2,1)ML and PR(1,2,3,3,2,1)ML systems is obtained and compared with that of a conventional 16/17(0,6/6)coded EPR4ML system. The result shows that PR(1,2,3,3,2,1)ML system has the best performance in high density recording

DOI： 10.11485/iteac.1999.0_11

CiNii Books

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

The performance evaluation of a PC coded PR4ML system recorded on two tracks using a spinstand is studied. It is compared with those of 16/17(0,6/6) coded E^2PR4ML system and a (1,7)RLL coded PR(1,2,1,-1,-2,-1)ML system. The results show that the proposed system exhibits the best BER performance among those systems.

DOI： 10.11485/iteac.1999.0_5

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

A searching method using genetic algorithm is studied for simplification of neural network equalizer. First, a model of read/write channel with partial erasure and a searching method using genetic algorithm are described. Then, the relationship between the required SNR to achieve a bit error rate of 10^<-4> and the reduction parameter for the 16/17 (0,6/6) coded EPR4ML system equalized by a simplified neural network is obtained by computer simulation and is compared with that of the conventional neural network equalizer. The results show that the performance of simplified neural network equalizer is equal to that of conventional neural network equalizer.

DOI： 10.11485/itetr.22.69.0_29

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

A new rate 9/10 trellis code matched to E^2PR4ML system for high density digital magnetic recording is proposed. The bit error rate performance of the TCPR system using a proposed code is obtained by computer simulation and it is compared with that of conventional 16/17 (0,6/6), 8/9 MTR coded E^2PR4ML systems. The results show that the proposed system exceeds performance of the conventional systems in high density recording. A bit error rate of 10^<-4> can be achieved with SNR of approximately 2.5,0.8dB less than the conventional 16/17 (0,6/6), 8/9 MTR coded E^2PR4ML systems at a normalized liner density of 3.

DOI： 10.11485/itetr.22.69.0_13

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

(1, 7)RLL符号, 8/9(0, 4/4)符号, 16/17(0, 6/6)符号の3種類の符号に対する各種PRML方式の性能について比較検討している.パーシャルイレージャのある高密度ディジタル磁気記録再生系において, PR4ML, EPR4ML, E^2PR4ML, ME^2PR4ML方式, PR(1, 1, 1, -1, -1, -1)ML, PR(1, 2, 1, -1, -2, -1)ML, PR(1, 2, 1, 0, -1, -2, -1)ML, 方式のビット誤り率を計算機シミュレーションにより求めた.その結果, (1, 7)RLL符号に対してはPR(1, 2, 1, -1, -2, -1)ML方式が, 8/9(0, 4/4), 16/17(0, 6/6)符号に対してはPR(1, 2, 1, 0, -1, -2, -1)ML方式が良好な特性を示すことが明らかとなった.

CiNii Books

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

The performance comparison of the various PRML systems for (1,7) RLL code, 8/9(0,4/4) code and 16/17(0,6/6) code is studied. The bit-error rates of PR4ML, EPR4ML, E^2PR4ML, ME^2PR4ML, PR(1,2,1,-1,-2,-1)ML and PR(1,2,1,0,-1,-2,-1)ML systems are obtained by computer simulation and the relationships between the reduction parameter in partial erasure and the required SNR are studied. The results show that PR(1,2,1,-1,-2,-1)ML system exhibits the good performance for (1,7) RLL code, and PR(1,2,1,0,-1,-2,-1)ML system offers the excellent performance for 8/9(0,4/4) code and 16/17(0,6/6) code.

DOI： 10.11485/itetr.22.54.0_37

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人映像情報メディア学会  

A seaching method using genetic algorithms is studied for the optimal tap configuration of nonuniformly spaced transversal filter in digital magnetic recording. A model of the recording/reproducing channel and the genetic algorithms are described. The bit-error rate (BER) performance of nonuniformly spaced transversal filter equalization for a PR4ML channel with partial erasure is obtained by computer simulation and is compared with that of conventional uniformly spaced transversal filter equalization. At a BER of 10^&lt;-4&gt;, the nonuniformly spaced transversal filter equalization yields a gain of 1.0dB over the conventional uniformly spaced transversal filter equalization.

DOI： 10.3169/itej.52.1501

CiNii Books

J-GLOBAL

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCRIPTA TECHNICA-JOHN WILEY & SONS  

A punctured convolutional coded PR4ML system for digital magnetic recording is proposed. In this system, convolutional coding is used for recording and two-track coded recording is carried out after using the punctured method. In this study, the error rate performance was simulated by a computer to compare this system with the conventional I-NRZI coded PR4ML system. Our system was found to have superior characteristics in high-density recording, and an error rate of 10(-4) could be achieved for a normalized linear density of K = 3, even when the SN ratio was about 3.8 dB lower at the reading point than in the conventional system. (C) 1998 Scripta Technica, Electron Comm Jpn Pt 2, 81(9): 62-70, 1998.

Web of Science

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

A method to construct trellis codes matched to class-4 partial response (PR4) and exteded class-4 partial response (EPR4) channels is studied. This coding method is based on the technique of set partitioning. In our method, all allowable output symbols from a partial response channel are defined as a signal constellation in Euclidean space and each subset decomposition of defined signal constellation is adopted in a multidimensional Euclidean space. Using this code construction technique, we can find optimal trellis coding and analyze a code structure easily and effectively. As a result of this coding technique, it is shown that the rate 9/10 trellis codes with a constraint length of 6 or 7 can provide about 2.4,2.3dB advantage over the conventional rate 8/9 (0,4/4) code in a PR4ML and 16/17 (0,6/6) code in an EPR4ML equalizations at a bit error rate of 10^<-4>, respectively.

DOI： 10.11485/itetr.22.30.0_1

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

The error rate performsnce of the fixed-delay tree search with decision feedback (FDTS/DF) system using a neural network instead of the conventional linear forward and feedback filters is studied. First, a model of the read/write channel with partial erasure and the FDTS/DF system with a neural network are described. Then, the bit-error rate of the FDTS/DF system using a neural network is evaluated by computer simulation and the performance is compared with that of the conventional FDTS/DF system with the linear forward and feedback filter. The results show that the proposed FDTS/DF system exhibits better performance than the conventional FDTS/DF system.

DOI： 10.11485/itetr.22.30.0_9

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

近年, ディジタル記録機器の高密度化の要望は高まる一方である.本論文では, 対象を磁気ディスク装置やディジタルVTRなどのディジタル磁気記録機器に限定し, その高密度を図るための手段としての信号処理技術について述べる.まず, その基礎となるパーシャルレスポンス方式, ビタビ復号法, PRML(Partial Response Maximum Likelihood)方式について詳述する.次いで, 長手磁気記録において最近盛んに検討されている各種信号処理方式について概観する.また, 高密度記録となるほど誤り率特性劣化の要因となるパーシャルイレージャ等の非線形ひずみを考慮した非線形ひずみ対応信号処理方式についても, 最近の研究動向を踏まえた検討を行い, 各種方式の性能評価を行う.更に, 将来の高密度記録方式として期待されている垂直磁気記録のための信号処理方式についても触れる.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

近年, ディジタル記録機器の高密度化の要望は高まる一方である.本論文では, 対象を磁気ディスク装置やディジタルVTRなどのディジタル磁気記録機器に限定し, その高密度化を図るための手段としての信号処理技術について述べる.まず, その基礎となるパーシャルレスポンス方式, ビタビ復号法, PRML(Partial Response Maximum Likelihood)方式について詳述する.次いで, 長手磁気記録において最近盛んに検討されている各種信号処理方式について概観する.また, 高密度記録となるほど誤り率特性劣化の要因となるパーシャルイレージャ等の非線形ひずみを考慮した非線形ひずみ対応信号処理方式についても, 最近の研究動向を踏まえた検討を行い, 各種方式の性能評価を行う.更に, 将来の高密度記録方式として期待されている垂直磁気記録のための信号処理方式についても触れる.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

ディジタル磁気記録における記録符号として, 符号化率11/12パンクチャド畳込み符号を用いたPRML方式を提案した.また, 計算機シミュレーションにより各種PRML方式に対する誤り率特性を求め, 8/9符号の場合と比較検討を行った.その結果, 本提案方式は8/9符号の場合に比べて高密度記録となるほど良好な特性を示すこと, および検討したPRML方式の中でE^2PR4ML方式が最良の性能を示し, 規格化線密度が3, ビット誤り率が10^-4において, 約3.4dBのSN比改善が得られることが明らかとなった.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

従来のPR4ML方式に対する8/10MSN符号は, 復号トレリスにおける準カタストロフィック系列の発生を制御できるがスライディングブロック復号器を必要とする符号構成となっていた.本論文では, 周期時変トレリス線図を用いて復号できる8/10MSN符号を新たに設計した.ここで提案する8/10MSN符号は, PR出力系列間の2乗ユークリッド距離の分布を改善し, 最小2乗自由ユークリッド距離をもつ系列の組合せを減少させることができる.また, ルックアップテーブルを参照するだけで符号系列とデータ系列を一意に復号でき, スライディングブロック復号器を不要とする.この結果, 本提案方式の8/10MSN符号化PR4ML方式は, 従来の方式に比べて, 規格化線密度3でビット誤り率10^-4において, 約0.8dBのSN比改善が得られることが明らかとなった.

CiNii Books

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

The performance evaluation of various PRML systems for (1,7)RLL code is studied with a PRML simulation system using a spinstand. The results show that PR(1,2,1,-1,-2,-1)ML, PR(1,1,1,-1,-1,-1)ML and PR(1,2,1,0,-1,-2,-1)ML systems exhibit good performance, and among them, PR(1,2,1,0,-1,-2,-1)ML system has the best performance in high density recording.

DOI： 10.11485/iteac.1998.0_132

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

The performance comparison of the various PRML systems for (1,7) RLL code, 8/9(0,4/4) code and 16/17(0,6/6) code is studied. The bit-error rates of PR4ML, EPR4ML, E^2PR4ML, ME^2PR4ML, PR (1,1,1,-1,-1,-1) ML and PR (1,2,1,0,-1,-2,-1) ML systems are obtained by computer simulation. The results show that PR (1,1,1,-1,-1,-1)ML system exhibits the good performance for (1,7) RLL code, and PR (1,2,1,0,-1,-2,-1) ML system offers the excellent performance for 8/9(0,4/4) code and 16/17(0,6/6) code.

DOI： 10.11485/itetr.21.75.0_1

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

The neural network equalization for the read/write data using a spin-stand is studied. As a recording code, the (1,7) RLL code is used and the readback waveform influenced by a nonlinear distortion in MR head is equalized to EPR4 characteristic by a three-layered neural network. For the read/write data at a recording density of 165 kFCI, the equalization characteristics and the bit-error rate of the EPR4ML sytem are obtained by computer simulation and are compared with those for a conventional Nyquist equalization. The results show that the neural network equalizer can effectively mitigate the effect of a nonlinear distortion in MR head and provide a significant performance improvement.

DOI： 10.11485/itetr.21.75.0_15

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

We have developed a simulation system to evaluate the performance of various PRML systems. The error rates of PR (1,0,-1) ML, PR (1,1,-1,-1) ML, PR (1,1,0,-1,-1) ML, and PR (1,2,0,-2,-1) ML systems for (1,7) RLL code are obtained by our simulation system, and performances are compared. The results show that PR (1,1,-1,-1) ML system exhibits good performance.

DOI： 10.11485/itetr.21.75.0_9

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

A simplification of a neural network equalization for a partial response maximum-likelihood (PRML) channel with a partial erasure and a nonlinear distortion in magneto-resistive (MR) head is studied. First, a model of the recording/reproducing channel with nonlinear distortions and the neural network equalizer are described. Then, the bit-error rates are obtained by computer simulation and the performances are compared with those of the conventional transversal filter and more complex neural network equlizer. The results show that the error rate performance of this simplified neural network equalizer is still better than that of the transversal filter.

DOI： 10.11485/itetr.21.75.0_23

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Language：English   Publishing type：Research paper (scientific journal)  

A punctured convolutional coded PR4ML system for digital magnetic recording, which applies a punctured coding method to the convolutional code and records the punctured code sequences on two tracks, is proposed. In this study, the bit error rate performance of the proposed system is obtained by computer simulation taking account of partial erasure, which is one of the nonlinear distortions at high densities, and it is compared with those of a conventional 8/9 coded PR4ML system and an I-NRZI coded PR4ML system. The results show that the proposed system is hardly affected by partial erasure and exhibits good performance in high-density recording. A bit error rate of 10-4 can be achieved with SNR&#039;s of approximately 13.2 dB and 9.1 dB less than those of the conventional 8/9 coded and I-NRZI coded PR4ML systems, respectively, at a normalized linear density of 3.

Scopus

CiNii Books

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCRIPTA TECHNICA-JOHN WILEY & SONS  

The performance of various PRML systems for (1,7)RLL code and 8/9 code is compared. First, the bit error rates are obtained by simulation for PR4ML, EPR4ML, PR(1,1,0,-1,-1)ML, and PR(1,2,1,0,-1,-2,-1)ML systems. Next, the relationships between the required SNR at the reading point to attain a prescribed error rate and the normalized linear density are derived and compared. Further, the performance of the FS-PRML system which can reduce the number of states of the Viterbi decoder for (1,7)RLL code to one half is compared. It is shown that the PR(1,2,1,0,-1,-2,-1)ML system and FS-PR(1,1,0,-1,-1)ML system for (1,7)RLL code exhibit excellent performance. (C) 1998 Scripta Technica.

Web of Science

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

ディジタル磁気記録において, 記録符号として畳込み符号を採用し, パンクチャド手法を用いたのち2トラックに記録再生する, パンクチャド畳込み符号化PR4ML方式を提案している. また, 計算機シミュレーションによりその誤り率特性を求め, 従来のI-NRZI符号化PR4ML方式の場合と比較検討を行った. その結果, 本提案方式は, 従来方式に比べ高密度記録において良好な特性を示し, 規格化線密度K=3において, 約3.8dB少ない読出し点のSN比で10&lt;-4&gt;の誤り率を達成できることを明らかにしている.

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

PR (1,2,3,2,1) ML system is proposed as a new (1,7) RLL coded partial response maximum likelihood (PRML) system for magneto-optical recording. Assuming that a magneto-optical recording system is linear and its impulse response is Gaussian, the error rate performance is obtained by computer simulation, and the performance is compared with that of conventional PR (1,2,2,1) ML system, which is well known for its good performance. The results show that the error rate performance of our system is better than that of PR (1,2,2,1) ML system.

DOI： 10.11485/itetr.21.57.0_17

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

In our PRML systems, we employ a noise whitening matched filter having minimum-phase to avoid emphasizing high frequency noise and coloring noise and combine it with Viterbi detector with path feedback. First, the minimum-phase, noise-whitening matched filter which consists made of a transversal filter and a low-pass filter is described. Then, the error rate performance is obtained by computer simulation, and the performance is compared with that of the combination of a minimum-phase, noise whitening matched filter and fixed delay tree search with decision feedback (FDTS/DF). The results show that Viterbi detector with path feedback can improve the signal-to-noise ratio over that of FDTS/DF.

DOI： 10.11485/itetr.21.36.0_27

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

A TCPR system for high density two track digital magnetic recording is proposed. In our system, a reduction in the channel rate due to convolutional coding is avoidable because a two track recording method improves the rate, and the number of ACS's in our system based on the syndrome decoding is fewer than that of the conventional Viterbi decoding. The results show that the proposed system keeps good performance in high density recording and saves SNR by about 3.6dB compared with the conventional NRZ coded PR4ML system at a normalized liner density of 3 and a bit error rate of 10^<-4>.

DOI： 10.11485/itetr.21.36.0_35

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

An application of the neural network canceller to the PR4ML channel with partial erasure is studied. First, a model of the read/write channel with partial erasure and a neural network canceller are described. Then, the bit-error rate of the PR4ML channel is evaluated by computer simulation and the performance is compared with that of the conventional neural network equalizer and Nyquist equalizer. The results show that the neural network canceller exhibits better performance than the conventional neural network equalizer and Nyquist equalizer.

DOI： 10.11485/itetr.21.36.0_43

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCRIPTA TECHNICA-JOHN WILEY & SONS  

The error rate of the partial response maximum-likelihood (PRML) system for a partial response channel with a (1 + D-l)(n)(1 - D-m) type transfer function in digital magnetic recording was systematically investigated. In this paper, first, the method of systematically finding a PRML system with a large signal-to-noise ratio (SNR) at the discrimination point and a large improvement of the SNR by Viterbi decoding is discussed. Using the result, a PRML system which shows an excellent performance is proposed. Next, a theoretical equation for the error rate is obtained as a function of the correlation between the noise sequences at the Viterbi decoder input and the error rate performance is compared. Using the results, it is shown that the PR(1, 2, 1, -1, -2, -1) system gives the best error rate performance. (C) 1997 Scripta Technica, Inc.

Web of Science

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

The PRML system using neural network canceller is proposed. The bit-error rate performance of the PR4ML channel with partial erasure is evaluated by computer simulation. It is shown that the neural network canceller exhibits better performance than the conventional neural network equalizer.

DOI： 10.11485/iteac.1997.0_102

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本磁気学会  

&amp;nbsp;&amp;nbsp;A method to improve the error rate performance of PRML systems with an Inter-symbol Interference (ISI) canceller having a tentative sequence detector is presented. The new system adopts a combination of a minimum phase noise whitening matched filter and a Viterbi detector with a path feedback scheme as a tentative detector. The result obtained by computer simulation shows that at a bit-error rate of 10&lt;sup&gt;-4&lt;/sup&gt;, the proposed systems improves the SNR by about 6.3 dB compared with the conventional EPR4ML system without an ISI canceller.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本磁気学会  

&amp;nbsp;&amp;nbsp;A neural network equalization for nonlinear distortion in magnetoresistive(MR) head is studied. First, a model of the recording/reproducing channel with MR head and neural network equalizer is described. Then, the bit-error rate(BER) for PR4ML system is obtained by computer simulation and the performance is compared with that of the conventional transversal filter equalization. It is shown that at a BER of 10&lt;sup&gt;-4&lt;/sup&gt;, the neural network equalization yields about 4.2dB gain over the transversal filter equalization.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本磁気学会  

&amp;nbsp;&amp;nbsp;An application of the neural network equalization to the partial response maximum-likelihood(PRML) channel with nonlinear distortion in magnetoresistive(MR) head and partial erasure is studied. First, a model of the recording/reproducing channel with the nonlinear distortion in MR head and partial erasure and the neural network equalizer are described. Then, the bit error rate(BER) performance for PRML channel is obtained by computer simulation and is compared with that of the conventional transversal equalizer. The results show that the BER performance of the neural network equalizer is better than that of the conventional transversal equalizer.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本磁気学会  

&amp;nbsp;&amp;nbsp;A neural network equalization of nonlinear channel with partial erasure is studied. First, a model of the recording/reproducing channel with partial erasure and a neural network equalizer are described. Then, the bit-error rate for PR4ML system is obtained by computer simulation and the performance is compared with that of the convention al Nyquist equalization. The results show that the error rate peformance of neural network equalization is better than that of Nyquist equalization.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本磁気学会  

&amp;nbsp;&amp;nbsp;Partial response maximum-likelihood(PRML) systems using an MR head and a double layer perpendicular medium are studied. The bit-error rate performance of PRML systems characterized by the polynomials with the positive coefficients for the (1,7) code and the negative coefficients for the 8/9 code is evaluated. The PRML system for the (1,7) code has a large minimum Euclidean distance and a small noise spectrum compared with those for the 8/9 code. This results in a significant performance improvement. Among PRML systems discussed in this study, PR(1, 2, 3, 2, 1)ML exhibits the best performance and improves the SNR by about 13.8 dB over that of PR4ML for the 8/9 code at a bit-error rate of 10&lt;sup&gt;&amp;minus;4&lt;/sup&gt; and a normalized linear density of 2.5. PR(1, 2, 2, 1)ML, PR(1, 3, 3, 1)ML and PR(1, 2, 1)ML also show excellent performance.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

(1,7)RLL符号と8/9符号に対する各種のPRML方式の性能について比較検討した.まず, PR4ML,EPR4ML, EEPR4ML, PR(1,1,0,-1,-1)ML, PR(1,2,1,0,-1,-2,-1)ML方式のビット誤り率をシミュレーションにより求めた.次いで,規定の誤り率を達成するのに要する読出し点の所要SN比と規格化線密度の関係を求め比較検討した.更に,(1,7)RLL符号に対するビタビ復号器の状態数を半減できるFS-PRML方式についても性能比較を行った.その結果,(1,7)RLL符号に対するPR(1,2,1,0,-1,-2,-1)ML方式およびFS-PR(1,1,0,-1,-1)ML方式が良好な特性を示すことが明らかとなった.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

The performance improvement of the partial response maximum-likelihood (PRML) system for (1, 7) runlength limited (RLL) code is studied. As a new PRML system, PR(1, 1, 0, -1, -1) system called modified E(2)PR4 (ME(2)PR4) Followed by Viterbi detector for (1, 7) RLL code is proposed. At first, a determination method of the tap weights in transversal filter to equalize to PR(1, 1, 0, -1, 1) characteristic taking account of a noise correlation is described. And the equalization characteristics of the transversal filter are evaluated. Then, a Viterbi detector for ME(2)PR4 utilizing the constraint of runlength of (1, 7) RLL code is presented. Finally, the bit-error rate is obtained by computer simulation and the performance is compared with that of the conventional PRML systems called PR4, EPR4 and E(2)PR4 systems with Viterbi detector. The results show that among these systems our system exhibits the best performance and the SNR improvement increases with the increase in the linear density.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

ディジタル磁気記録において(1+D^l)^n(1-D^m)形の伝達関数を有するパーシャルレスポンスチャネルに対するPRML (Partial Response Maximum Likelihood)方式の誤り率を体系的に検討する手法について述べている.まず,識別点SN比が大きく,かつビタビ復号によるSN比改善度も大となるようなPRML方式を体系的に見出す方法について述べ, これにより得られた良好な特性を示す可能性のあるPRML方式がいくつか提案されている.次いで, これらの方式の誤り率の理論式をビタビ復号器入力における雑音系列の相関関数の関数として求め,それらの誤り率特性を比較検討した.その結果, PR(1,2,1,-1,-2,-1)方式が最良の誤り率特性を示すことが明らかとなった.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

For perpendicular magnetic recording by a bi-layered main-pole head which shows an excellent linearity, the perfor mance of PRML system combining partial response (PR) system with maximum likelihood (ML) decoding is studied. The bit-error rate of the PRML system using a PR(I,I,0,0,0,0, - 1, - 1) system is obtained by computer simulation and compared with that of the conventional PRML system. It is shown that our PRML system exhibits better performance than the conventional PRML system in high density recording.

DOI： 10.1016/0304-8853(95)01222-2

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

An application of neural network equalization to the partial response maximum-likelihood(PRML) channel with partial erasure in high density digital magnetic recoding is studied. The bit-error rate performance is evaluated by computer simulation. It is shown that our system shows better performance than the conventional PRML system with Nyquist equalization.

DOI： 10.11485/tvac.32.0_385

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

This report describes a new rate 10/12 MSN code for PRML system in a high density digital magnetic recording. The result shows that a proposed MSN code for PR(1,0,-1)ML provides about a 0.9dB advantage compared with the conventional rate 8/10 MSN code at a symbol-error rate of 10^<-4>.

DOI： 10.11485/tvac.32.0_383

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

Simplification of the Viterbi algorithm and the error rate performance are presented for a partial response maximum-likelihood (PRML) system employing the PR(1,1) system as a PR system for (1,7) run-length limited (RLL) code. The minimum run-length of 1's or 0's in the output sequence of the precoder for (1,7) RLL code is limited to 2. Two kinds of simplified Viterbi algorithms using this run-length constraint are proposed. One algorithm requires the path memory length of only two in the Viterbi detector. The Viterbi detector based on the other algorithm is equivalent to the simple PR(1,1) system followed by a threshold detector. The bit-error rates of PRML systems with Viterbi detectors based on these algorithms are obtained by computer simulation and their performance is compared with that of conventional PRML systems for (1,7) RLL code. It is shown that the proposed PRML system exhibits better performance than conventional PRML systems at high recording density.

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

This report describes a study on applying ISI (intersymbol interference) canceller to PRML system in high density digital magnetic recording. And it is shown that our system has better performance than conventional PR-IV and EPR-IV systems with Viterbi detector.

DOI： 10.11485/tvac.31.0_25

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Language：English   Publishing type：Research paper (scientific journal)  

A new partial response (PR) channel which contains the write equalizer in addition to conventional PR channel is proposed. Our write equalizer outputs DC-free waveforms of two levels. Our read equalizer can reduce high-frequency noise, and what is more, it has little degradation of eye opening. The PR channels in combination with Viterbi decoder give partial response maximum-likelihood (PRML) systems which exhibit a good performance. The bit error rates for several PRML systems are obtained by computer simulation, where a Lorentzian channel with additive white Gaussian noise is assumed. The results shows that PR(1,1,-1,-1) system has an excellent performance in high density recording for a system in which the small transition spacings required by our write equalization is allowed. © 1995 IEEE

DOI： 10.1109/20.364788

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCRIPTA TECHNICA PUBL  

The error-rate performance of the partial response maximum likelihood (PRML) system combining the partial response (PR) system with the Viterbi decoding, which is a type of maximum likelihood (ML) decoding, is investigated in perpendicular magnetic recording using a multilayered main-pole head. Waveform approximation is carried out with regard to the isolated reproducing waveform obtained by experiment; and, based on this, the bit error rate is determined by computer simulation.
First, taking into account the noise increase due to equalization, the signal-to-noise ratio (SNR) at the discrimination point and the bit error rates of bit-by-bit decoding of several PR systems using the characteristics of the multilayered main-pole head are determined. Next, the bit error rates of the PRML system are determined for these PR systems and then compared with those for the conventional PR system. Then it is clarified that the best performance is obtained by the PR(1, 0, 0, 0, -1) system among these PR systems, and the improvement of SNR compared with the conventional PR system is about 1.9 dB in the case of the bit-by-bit decoding system and 4. 1 dB in the case of the PRML system at an error rate of 10(-4).

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Language：Japanese   Publisher：一般社団法人電子情報通信学会  

PR(1,1,-1,-1)とPR(1,1,0,-1,-1)方式の二つのパーシャルレスポンス方式について,ビタビ復号器入力における雑音系列の相関係数の関数として誤り率の上界を導出し,これによる理論値とシミュレーション値を比較検討している.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

複合膜主磁極形単磁極ヘッドを用いた垂直記録において,パーシャルレスポンス(PR)方式と最ゆう復号法の一種であるビタビ復号法とを組み合せたPRML(Partial Response Maximum-Likelihood)方式の誤り率特性について検討している.その際,実験により得られた孤立再生波形に対して波形近似を行い,これをもとにしてシミュレーションにより誤り率を求めている.まず,等化による雑音増大を考慮に入れて,複合膜主磁極形単磁極ヘッドの特性を利用したいくつかのPR方式の識別点SN比とビットごとの復号法の誤り率を求めている.次いで,これらのPR方式に対するPRML方式の誤り率を求め,従来のPR方式の場合と比較検討している.そして,これらPR方式のうちで最良の特性が得られるのはPR(1,0,0,0,-1)方式であり,10^&lt;-4&gt;の誤り率において,従来のPR方式の場合に比べビットごとの復号法の場合で約1.9dB,PRML方式の場合で約4.1dBのSN比改善が得られることを明らかにしている.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCRIPTA TECHNICA PUBL  

This paper proposes the (4, 5, 6)/11 code, which is a new n/m code, constrained in that the minimum runlength of symbol ''0'' in the codeword is 2 and is suited to PR(1, 1) equalization. In PR(1) equalization, a pseudo-PR(1, 1) characteristic is obtained by shifting the sampling points by T-S/2 (where T-S is the symbol interval). Assuming that the conventional Viterbi decoding is applied to the (4, 5, 6)/11 code, the error-rate characteristic is examined by simulation, and the result is compared to that of the well-known 4/11 code. It is shown as a result that the(4, 5, 6)/11 code has an excellent performance. Then a modified Viterbi decoding is considered by utilizing the run-length constraint, and the performance is evaluated.
The colored noise sequence is approximated by a simple Markov process and another modified Viterbi decoding utilizing the correlation of the noise sequence also is considered. It is shown as a result that the CN ratio is improved compared to the conventional Viterbi decoding by about 1.0 dB in the former and about 2.7 dB in the latter, at the error rate of 10(-4).

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Language：English   Publishing type：Research paper (scientific journal)  

The error‐rate performance of the partial response maximum likelihood (PRML) system combining the partial response (PR) system with the Viterbi decoding, which is a type of maximum likelihood (ML) decoding, is investigated in perpendicular magnetic recording using a multilayered main‐pole head. Waveform approximation is carried out with regard to the isolated reproducing waveform obtained by experiment
and, based on this, the bit error rate is determined by computer simulation. First, taking into account the noise increase due to equalization, the signal‐to‐noise ratio (SNR) at the discrimination point and the bit error rates of bit‐by‐bit decoding of several PR systems using the characteristics of the multilayered main‐pole head are determined. Next, the bit error rates of the PRML system are determined for these PR systems and then compared with those for the conventional PR system. Then it is clarified that the best performance is obtained by the PR(1, 0, 0, 0, ‐1) system among these PR systems, and the improvement of SNR compared with the conventional PR system is about 1.9 dB in the case of the bit‐by‐bit decoding system and 4.1 dB in the case of the PRML system at an error rate of 10−4. Copyright © 1994 Wiley Periodicals, Inc., A Wiley Company

DOI： 10.1002/ecjb.4420770808

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Language：Japanese   Publisher：一般社団法人電子情報通信学会  

ディジタル磁気記録においてトランスバーサルフィルタによりPR(1,1,0,-1,-1)方式を得るときの等化特性について検討を行っている.高域遮断による影響も考慮に入れてトランスバーサルフィルタのタップ係数を定めるこにより,等化特性の改善が得られることを示している.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

優れたDCフリー符号として知られているM^2符号に対する積分検出方式において,高域ノイズを抑圧するために行う帯域制限により生ずるアイの劣化を記録波形の反転位置を制御することで補償する手法を提案している.まず,計算機シミュレーションにより描いたアイパターンからアイ開口率,タイミングマージンを求め,本手法により,改善が可能であることを示している.次いで,ビット誤り率を計算機シミュレーションから求め,補償がない場合に比べて本手法では,10^&lt;-4&gt;の誤り率を約2.2dB少ないSN比で達成できることを明らかにしている.

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Language：Japanese   Publisher：一般社団法人電子情報通信学会  

3B-2T符号に対して2値記録波形を割り当てる擬似的な3値記録方式を提案している.そして,PR(1,0,-1)方式における所定の誤り率を達成するのに要する読出し点SN比を求め,ACバイアスによるチャネルの線形化を仮定した場合と比較検討を行っている.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

符号語内でのシンボル&quot;0&quot;の最小ラン長が2となる制約をもち,PR(1,1)形の等化に適した新たなn/m符号である(4,5,6)/11符号を提案している.PR(1)等化におけるサンプリング時点をT_s/2(ここに,T_sはシンボル間隔を表す)ずらせることによって,擬似的なPR(1,1)特性が得られる.(4,5,6)/11符号に対する従来のビタビ復号法の誤り率特性のシミュレーションにより求め,良く知られた4/11符号の特性と比較している.その結果,(4,5,6)/11符号はすぐれた特性を示すことが明らかとなった.次いで,ラン長の制約を利用した修正ビタビ復号法の特性を求めている.また,有色雑音系列を単純Markov過程で近似し,雑音系列の相関を利用した別の修正ビタビ復号法についても検討している.その結果,10^,&lt;-4&gt;の誤り率における従来のビタビ復号法に対するCN比の改善度は,前者の場合で約1.0dB,後者の場合で2.7dBとなることが示されている.

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Language：English   Publishing type：Research paper (scientific journal)  

The partial response (PR) system is believed to be an important scheme for signal processing in high‐density digital magnetic recording. This paper discusses the improvement in performance of the PR(1, 0m ‐ 1, ‐1) system, which is one of the PR systems. With increasing recording density, a high‐frequency noise due to the compensation for a high‐frequency attenuation increases significantly and accordingly a signal‐to‐noise ratio (SNR) becomes lower, which is also tied to the inherent high‐frequency boost characteristics of PR(1, 0m ‐ 1, ‐1). Also proposed is a new PR system and a signal‐detection method by which one can expect to improve the characteristics by using an intersymbol interference for a signal detection caused by suppressing a high‐frequency noise through a bandwidth limitation in PR(1, 0m ‐ 1, ‐1). For the proposed system and the conventional PR(1, 0m ‐ 1, ‐1) system, the SNR required to achieve a bit error rate of 10−8 is obtained. It is confirmed that the proposed system provides a better performance than the conventional system. Copyright © 1993 Wiley Periodicals, Inc., A Wiley Company

DOI： 10.1002/ecjb.4420760606

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Language：Japanese   Publisher：電子情報通信学会エレクトロニクスソサイエティ  

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Language：Japanese   Publisher：一般社団法人映像情報メディア学会  

DC freeing of the write waveform is an important technique in digital magnetic recording. The higher the recording density is, the stronger the effect of high frequency noise becomes. We use the DC-freeing technique of write equalization to boost high frequency on the write side, and read equalization with which we can reduce high-frequency noise with little degradation of the eye opening, is adopted on the read side. In addition, we adopt Viterbi decoding as a decoding method for further improvement. In this paper, we report the synthesis of this write and read equalization method. Computer simulation shows that our system has an excellent error rate performance compared with the well-known combination of NRZ recording code and integrated detection.

DOI： 10.3169/itej1978.46.1234

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Language：Japanese   Publisher：電子情報通信学会エレクトロニクスソサイエティ  

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

The influence of the correlation coefficients of colored noise on the error rate performance of PRML system is studied. For two partial response systems, PR(1,1,-1,-1) and PR(1,1,0,-1,-1) systems, the upper bounds on error rates are derived and expressed as a function of the correlation coefficients of noise sequnces at the input of Viterbi decoder. The theoretical value of error Fate is also compared with the simulated and the result shows that there is close agreement between them. Furthermore, the relationship between the correlation coefficient of colored noise and the error rate performance is clarified.

DOI： 10.11485/tvtr.16.72_25

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

EPR-IV system is known as the partial response (PR) system which shows an excellent performance. PR (1,1,0,-1,-1) system is proposed here and the performance is compared with that for EPR-IV system. It is shown that at a bit-error rate of 10^<-4> PR (1,1,0,-1,-1) system saves SNR by about 1.9dB compared with EPR-IV system.

DOI： 10.11485/tvac.28.0_81

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Language：English   Publishing type：Research paper (scientific journal)  

An efficient butt-joined coupling scheme between single-mode planar waveguides with different refractive index profiles is proposed. The configuration consists of tapered waveguide with nonlinear cladding. Power dependent coupling efficiency of the configuration is analyzed by the beam propagation method. The numerical results show that this configuration has high-coupling efficiency and is less sensitive to the offset between coupled waveguides if the input power is properly selected. © 1992 IEEE

DOI： 10.1109/68.127221

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An efficient coupling scheme between single-mode planar waveguides with different film thickness is proposed. The configuration consists of a tapered waveguide with nonlinear cladding. Power-dependent coupling efficiency of the configuration is analyzed by the beam propagation method. The numerical results show that this configuration has high coupling efficiency and is less sensitive to the offset between coupled waveguides when the input power is properly selected. © 1992 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.31.1565

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：電子情報通信学会  

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

DOI： 10.11485/ncrtv.21.0_215

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

DOI： 10.11485/ncrtv.21.0_219

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：電子通信学会  

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

DOI： 10.11485/tvtr.8.37_7

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Language：Japanese   Publisher：The Institute of Image Information and Television Engineers  

DOI： 10.11485/ncrtv.19.0_161

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Language：Japanese   Publisher：東京 : 電子情報通信学会  

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Other Link： http://id.ndl.go.jp/bib/029084816

Language：Japanese   Publisher：東京 : 映像情報メディア学会  

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Other Link： http://id.ndl.go.jp/bib/029116208

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