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