Yukari Katayama

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.

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.

Rate 8/14 asymmetrical DC control code for optical disks

A new run-length-limited (RLL) code for optical disks is described. It is a rate 8/14 asymmetrical (d1,d2,k)=(2,1,11) code that has a better detection window size. Compared to the EFMPlus code, the ARL code has a 1.6 dB gain in the required SNR at a BER of 10/sup -4/.