Takushi Nishiya

Turbo-EEPRML: An EEPR4 channel with an error-correcting post-processor designed for 16/17 rate quasi-MTR code

An EEPRML channel with a post processor has been developed for compensating for the degradation in performance due to noise correlation. This Turbo-EEPRML is designed for 16/17 rate quasi-MTR (QMTR) code. The proposed method has high performance and simple circuitry. Simulation showed that Turbo-EEPRML has a 2.0-2.5 dB coding gain over a conventional EPRML channel for 16/17 GCR code.

Rate 16/17 maximum transition run (3;11) code on an EEPRML channel with an error-correcting postprocessor

A rate 16/17 maximum transition run (MTR) (3;11) code on an EEPRML channel with a postprocessor (turbo-EEPRML) has been developed. The postprocessor compensates for the degradation in performance due to noise correlation. The proposed method has high performance and simple circuitry. Simulation results showed that the rate 16/17 MTR (3;11) code on a turbo-EEPRML channel has a performance gain of 1.0-4.0 dB over a conventional extended partial response maximum likelihood channel with the rate 16/17 run-length-limited code.

PERD: partial error response detection

Extended Partial Response Maximum Likelihood (EPRML) detection outperforms PRML detection on very high-density magnetic recording channels but is much more complex than PRML and is difficult to implement for high data rates. PERD is an alternative to the EPRML detector which gives even better performance. It consists of a conventional PRML detector and a pattern discrimination circuit operating on the error waveform between the waveform estimated from the PRML outputs and the actual playback waveform. A bit-by-bit simulation confirms the expected performance gains over PRML detection.

Two-dimensional run-length-limited code and partial response maximum likelihood system with multi-track recording

In optical disk systems, user data is recorded along a continuous spiral track by using 1D run-length-limited (RLL) codes. Track pitch and bit pitch are strongly related to the wavelength of the laser and the numerical aperture (NA) of the lens. A narrower track pitch or bit pitch increases cross-talk and degrades the signal to noise ratio (S/N). Certain phase-change optical disk formats adopt land and groove recording, because the phase difference of the light reflected from adjacent tracks decreases cross-talk. A cross-talk cancellation scheme using 2D equalization has been studied (Y. Tomita et al, Jpn. J. Appl. Phys., vol. 40, pt. 1, no. 3B, pp. 1716-1722, 2001). Canceling cross-talk is one way to increase recording density. However, if inter-track interference (ITI) remaining in the read-out signal increases, amplification of noise at the filter of the cross-talk canceller increases. Thus, for extremely high-density recording, the read-write and detection method should incorporate a means of dealing with heavy ITI. In this paper, we propose a 2D RLL code and a 2D partial response maximum likelihood (PRML) system that has the potential to increase media capacity of next-generation optical disk systems without significantly changing the laser wavelength or the lens NA.

Application of the intelligent alarm system for the plant operation

Abstract A new alarm system which provides a qualitative description of process data trends is presented in this paper. This description is based on a method of marking process data with significant words. The objectives of this system are (1)automatically to recognize a fluctuation on a process instead of plant operators, and (2)to develop a fundamental technique for data trends monitoring systems by using a qualitative description. Recently, this system was used to catch a fluctuation on a real process before it became dangerous situation. Finally, more applications of using a qualitative description for the plant operators which will be developed in the near future, and the method of detecting a reasonable fluctuations are presented.

A PRML and EPRML spliced operation scheme designed to reduce power dissipation of read channel chips

In order to reduce the power dissipation and the circuit size for read channel chips, two techniques are proposed. One is based on the spliced operation of two different channel signaling methods such as PRML and EPRML. These two detectors are operated selectively in correspondence with the value of the reliability information extracted from the data series. The other is an extended method which applies the transformed trellis simplification technique to a RADIX4 detector. These are effective for implementing a high data transfer rate. We have confirmed that the total detector power dissipation including PRML, EPRML and additional circuits is reduced to less than half of the conventional EPRML power dissipation, while achieving twice the data transfer rate of the conventional EPRML.

Simplified EEPR Viterbi detector based on a transformed radix-4 trellis for a disk drive

A simplified EEPR Viterbi detector based on a transformed radix-4 trellis using 16/17 maximum transition run (MTR) code is developed. The transformed radix-4 trellis is a radix-4 trellis applying the transformed trellis in order to reduce complexity. The proposed Viterbi detector also applies a new simplification method that eliminates low likely states according to the equalized data (inputs of the detector). By this simplification, the ACS circuit size can be reduced to 60% as compared to the original radix-4 Viterbi detector. Moreover, the necessary path memory length for the Viterbi detector is theoretically derived by estimating the probability of the error patterns which can occur on the EEPRML channel using the 16/17 MTR code. Simulations show that the performance of the simplified Viterbi detector does not degrade on such a channel. The proposed simplification of the Viterbi detector is a useful way to implement the high-speed and low-power EEPR Viterbi detector.

A digital servo architecture with 8.8 bit resolution of position error signal for disk drives

A new digital servo signal processing architecture with 8.8 bit resolution of position error signal for disk drives is presented. It achieves an 8.8 bit resolution of the position error signal by use of a 6 bit ADC (analog to digital converter) for the data channel. This new architecture uses only a full wave rectifier and a divider. The burst signal is rectified in the analog domain before being sampled by the clock, which has a higher frequency than the servo frequency, in the ADC.

Random seed scrambling method for high density phase change optical discs

Repeatedly rewriting the same channel bit pattern at the same location on a phase-change optical disc usually causes the media to deteriorate. To prevent this, the random bit shift of 128-bit and the free polarity of NRZI-converted pulses were introduced into the DVD-RAM system. However, these measures cause difficulty in the timing control at writing starts and. complication of the control of circuits. So in this paper, a new scrambling method, the Random Seed Scrambling Method is proposed. In this method, the data is scrambled using a different seed each time the data is written, so the different data is over-written at the location each time. The method of random seed scrambling has a unique characteristic that the seed is not necessary to de-scramble the scrambled data. By using this method, the amount of the high density phase-change optical disc wear is reduced.

Performance evaluation of asymmetrical run-length-limited code for optical disks

A performance comparison between a rate 8 / 14 asymmetrical run-length-limited (RLL) code and the EFMPlus code for optical disks is described. The limited condition of the rate 8 / 14 asymmetrical code is. This code has a better detection window size than the EFMPlus code because of the 14.3 percent greater efficiency of its coding rate. We describe the bit error rate (BER) performance and the tilt and defocus tolerance of the rate 8 / 14 ARL code. Compared to the EFMPlus code, the rate 8 / 14 ARL code has a 0.7-dB gain in the required S / N at a BER of 10-4. The rate 8 / 14 ARL code is also more robust against tilt and defocus.