Modified viterbi algorithm for a jitter-dominant 1-D/sup 2/ channel

Abstract

As transitions are packed closer at high recording densities, transition noise becomes significant, and the detection performance of the Viterbi algorithm (VA) is substantially degraded. The random jitter of the written transition position is an important contribution to the transition noise. Because of its data-dependency, jitter cannot be modeled as an additive noise. In this paper, we propose a practical detection scheme based on the maximum likelihood (ML) criterion under the assumption of Gaussian jitter. This detection scheme is very similar to the VA except that a modified branch error metric is used to incorporate the data-dependent nature of jitter noise. Error rate simulations are performed for channels dominated by either Gaussian jitter or truncated Gaussian jitter. The results show that the proposed detection scheme yields lower error rates than the VA.