Noise predictive maximum likelihood detection combined with parity-based post-processing

Abstract

The performance of magnetic recording systems that include conventional modulation codes combined with multiple parity bits is studied. Various performance measures, including bit error rate at the output of the inverse precoder, byte error probability at the input of the Reed-Solomon (RS) decoder and sector error rate, are used to evaluate the performance of various coding/detection schemes. Suboptimum detection/decoding schemes consisting of a 16-state noise-predictive maximum-likelihood (NPML) detector followed by parity-based noise-predictive post-processing, and maximum-likelihood sequence detection/decoding on the combined channel/parity trellis are considered. For conventional modulation codes, it is shown that although the dual-parity post-processor gains 0.5 dB over the single-parity post-processor in terms of bit-and byte-error-rate performance, the sector-error-rate performance of both schemes is almost the same. Furthermore, the sector-error-rate performance of optimum 64-state combined channel/parity detection for the dual-parity code is shown to be approximately 0.1 dB better than that of optimum 32-state combined channel/parity detection for the single-parity code. These performance gains can be even more substantial if appropriate coding techniques that eliminate certain error events and minimize error burst length or multiparity codes in conjunction with combined parity/channel detection are used.Index Terms-Noise-predictive maximum-likelihood detection, noise-predictive post-processing, parity check codes, sector error probability.

Noise Correlation-Aided Iterative Decoding for Magnetic Recording Channels

“…3 and 4 illustrate the BER performance of the three decoding schemes in comparison to that of the benchmark scheme in [18] and to the Noise Predictive Turbo Systems with Hard Feedback (NPTS/HF) proposed in [15] (here we used the linear prediction order of 3), at recording densities of 2.25 and 2.86, respectively. The recording densities of 2.25 and 2.86 which lie in the typical operational range of the recoding densities used for PR-4-equalized Lorentzian channels [8]- [10], [24], [26], are selected for the sake of comparison. As we can see, all three decoding schemes exhibit a significant performance improvement over the benchmark scheme.…”

Error Event Corrections Using List-NPML Decoding and Error Detection Codes

“…However, post processors are suboptimum solutions and usually not robust to miscorrection of error events. In addition, it is reported that post-ECC gains are not as much as the pre-ECC gains [5]. We note that the frequency of occurrences of such error events are functions of system parameters such as the recording density and the physical conditions of the read/write heads and media.…”

“…Such schemes combined with various detection codes are shown to be helpful when the frequency of error-event occurrences at the output of the NPMLD is uneven and known to the post processor, as discussed in [5] and [6]. One of the advantage of the post processing is the low complexity implementation.…”

Parity-check codes and post-processing for d=1 optical recording channels

“…N recent years, the parity-check (PC) codes and post-Viterbi error correction processing based detection approach [1] has found wide acceptance in magnetic recording systems since it can correct dominant short error events at the channel detector output using only a few parity bits, and thereby significantly reduce the correction capacity loss of the error correction code (ECC). In this paper, we propose various PC codes in conjunction with improved post-processing for constrained optical recording systems (i.e., Blu-ray disc (BD) [2] or high-definition digital versatile disc (HD-DVD) [3]).…”