• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.9C
• /
• pp.840-845
• /
• 2006

This paper presents a partial response maximum likelihood (PRML) detection method using partial response signal-to-noise ratio (PRSNR) that evaluates the signal quality of asymmetric optical recording channel. It is confirmed that the equalizer maximizing the PRSNR value can be most properly adapted to the asymmetric optical recording channel. The proposed PRML detection using this result has 1.8dB SNR gain at $8.5{\times}10-5$ bit error rate compared to PRML detection using typical adaptive equalizer.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.12C
• /
• pp.1601-1605
• /
• 2004

When codeword sequence has two or less successive transitions, the performance of 4th-order partial response maximum-likelihood (PRML) detector can be improved. However, the code leads to an unacceptable loss of performance due to the low code rate. For a rate 718 code that MTR constraint (i) of each codeword is limited to 2, and j is allowed to be 3 when codewords are connected, we modified the trellis of PRML detector to combine j=2 with J=3. We confirmed that the rate 718 coded 4th-order PRML detection with combined trellis achieves the SNR gain more than 2dB compared to the rate 819 coded 4u_order PRML detection at 10-s BER in high-density longitudinal or perpendicular magnetic recording systems.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.3C
• /
• pp.77-82
• /
• 2005

Partial response maximum likelihood (PRML) detection using the Viterbi algorithm involves the calculation of likelihood metrics that determine the most likely sequence of decoded data. In general, it is assumed that branches at each node in the trellis diagram have same probabilities. If modulation code with minimum and maximum run-length constraints is used, the occurrence ratio (Ro) of each particular pattern is different, and therefore the assumption is not true. We present a calculation scheme of the likelihood metrics for the PRML detection using the occurrence ratio. In simulation, we have tested the two (1,7) run-length-limited codes and calculated the occurrence ratios as the orders of PR targets are changed. We can identify that the PRML detections using the occurrence ratio provide more than about 0.5dB gain compared to conventional PRML detections at 10/sup -5/ BER in high-density magnetic recording and optical recording channels.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.10C
• /
• pp.927-932
• /
• 2006

We Propose a partial response maximum likelihood(PRML) detection method that improves the performance of the high-density optical storage system. It concurrently adjusts the coefficient of equalizer and reference values of branches in Viterbi detector. For the estimation of asymmetric channel characteristics by the tangential tilt, we exploit sync patterns in each data frame. The simulation result shows it improves the Performance up to 4dB at 10-6 BER compared to conventional adaptive PRML.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.9C
• /
• pp.871-876
• /
• 2005

In this paper, we propose an improved partial response maximum likelihood (PRML) detection scheme that has an adaptive equalizer and can be applied in the asymmetric optical recording system with high-density. We confirmed that the proposed PRML detector improves detection performance. In addition, we implemented the detector by Verilog HDL. The adaptive equalizer is composed of tap coefficient updating unit using LMS algorithn and FIR filter. FIR filter is implemented by the transposed direct form architecture for high speed operation. Viterbi detector is implemented by the register exchange method.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.7C
• /
• pp.642-646
• /
• 2005

We propose an improved partial response maximum likelihood (PRML) detector with the branch value compensation of Viterbi decoder for asymmetric high-density optical channel. Since the compensation value calculated by a survival path is applied to each branch metric, it reduces the detection errors by the asymmetric channel. The proposed PRML detection scheme improves the detection performance on the $2^{nd},\;3^{rd}\;and\;4^{th}$ order PR targets for asymmetric optical recording channel.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.5 no.5
• /
• pp.454-457
• /
• 2004

Partial response maximum likelihood (PRML) is a powerful and indispensable detection scheme for perpendicular magnetic recording channels. The proposed method is a low complexity detection scheme which is related to the PRML system. The simulation results show that PR(1,2,3,4,3,2,1)ML and PR(l,2,3,3,2,1)ML using modulation encoding with R=2/3 have the most improved performance at K=3,4. However, in the case of K=3, R=2/3 PR(1,1,1,1)ML effectively reduces the complexity compared to PR(1,2,3,3,2,1), but it has L5dB performance degradation at most. In the case of K=4, R=l PR(1,2,2,1)ML has very low complexity compared to R=2/3 PR(l,2,3,4,3,2,1)ML. but it has about 2dB performance degradation at most.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.3C
• /
• pp.59-63
• /
• 2005

We propose non-DC-free generalized PRML (GPRML) that are suppressed DC contents for matching to the response of perpendicular magnetic recording channel with a ring-head. In addition, DC-free encoding is considered to prevent low-frequency disturbances. The SNR performance is obtained by combining the various PRML channels with DC-free and non-DC-free codes during the normalized recording density increases from 2.5 to 3.5. The GPRML detections without using DC-free code get SNR gains more than 1dB compared to the conventional PRML systems at 10/sup -5/BER. We confirmed that the rate 127/136 DC-free coded GPRML systems show good performances compared with the 16/17 non-DC-free coded GPRML systems. In results, DC-free coded GPRML detections get gains about 1.4dB and 2.0dB at the density of 3.3 and 3.5, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.11C
• /
• pp.1052-1057
• /
• 2006

The implement the adaptive partial response maximum likelihood (PRML) detector with tilt analyzer for asymmetric high-density optical storage system. For the estimation of disc tilt, we exploit spc patterns in each data frame. Because of using the ROM table to renew the coefficients of equalizer and reference values of branches, the complexity of the hardware is reduced. The proposed PRML has been designed and verified by VerilogHDL and synthesized by the Synopsys Design Compiler with Hynix $0.35{\mu}m$ STD cell library. In the result, the total gate count is 35K, and the maximum operating frequency is 140MHz.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.9C
• /
• pp.891-897
• /
• 2003

Partial response maxim likelihood (PRML) is a powerful and indispensable detection scheme for perpendicular magnetic recording channels. The performance of PRML can be improved by incorporating a noise prediction scheme into branch metric computations of Viterbi algorithm (VA). However, the systems constructed by VA have shortcomings in the form of high complexity and cost. In this connection, a new simple detection scheme is proposed by exploiting the minimum run-length parameter d=1 of RLL code. The proposed detection scheme have a slicer instead of Viterbi detector and a noise predictor as a feedback filter. Therefore, to improve BER performance, the proposed detection scheme is extended to dual detection scheme for improving the BER performance. Simulation results show that the proposed scheme has a comparable performance to noise-predictive maximum likelihood (NPML) detector with less complexity when the partial response (PR) target is (1,2,1).