Multihead Multitrack Detection With Reduced-State Sequence Estimation

Abstract

Abstract-To achieve ultra-high storage capacity, the data tracks are squeezed more and more on the magnetic recording disks, causing severe intertrack interference (ITI). The multihead multitrack (MHMT) detector is proposed to better combat ITI. Such a detector, however, has prohibitive implementation complexity. In this paper we propose to use the reduced-state sequence estimation (RSSE) algorithm to significantly reduce the complexity, and render MHMT practical. We first consider a commonly used symmetric two-head two-track (2H2T) channel model. The effective distance between two input symbols is redefined. It provides a better distance measure and naturally leads to an unbalanced set partition tree. Different trellis configurations are obtained based on the desired performance/complexity tradeoff. Simulation results show that the reduced MHMT detector can achieve near maximum-likelihood (ML) performance with a small fraction of the original number of trellis states. Error event analysis is given to explain the behavior of RSSE algorithm on 2H2T channel. Search results of dominant RSSE error events for different channel targets are presented. We also study an asymmetric 2H2T system. The simulation results and error event analysis show that RSSE is applicable to the asymmetric channel.

Utilization of multiple read heads for TMR prediction and correction in bit-patterned media recording

“…[5][6][7] Moreover, a practical multi-head multi-track (MHMT) detector 5 that provides a low-complexity approach to adaptively estimate the time-varying ITI was presented. In general, the MHMT detector can handle the ITI effect better than a single-head single-track detector.…”

“…In general, the MHMT detector can handle the ITI effect better than a single-head single-track detector. Thus, the reduced state sequence estimation algorithm 6 to significantly decrease the complexity of the MHMT detector was discussed. G. Mathew 7 et.…”