Estimation of areal density gains of TDMR system with 2D detector

Two-dimensional magnetic recording (TDMR) is expected to drive continued areal density growth of hard-disk drives (HDDs) as the growth for conventional perpendicular magnetic recording (PMR)-based HDDs is slowing down. Feasibility of manufacturing more than one reader in a single head has hastened the development of TDMR and considerable effort is underway in developing read channels that can exploit the availability of multiple readers. First generation of TDMR-based HDDs will likely derive its gains from the SNR improvement obtained by combining multiple readback signals to remove inter-track interference (ITI). In this case, data belonging to a single track of interest is subsequently detected. A natural extension to this system is to combine the readback signals without removing ITI and jointly detecting data belonging to two tracks using a two-dimensional detector. Under the assumption that tracks are written synchronously, in this paper, we explore from a systems perspective if further areal density gains can be obtained from such a system. We employ a grain-based channel model for our investigation and estimate gains by appropriate optimization of the dual-reader systems, including optimizing reader placement. Furthermore, for the set of reader placement configurations, which affords reliable detection of both tracks, we introduce a new coding scheme called cross-track coding and show that additional areal density gains can be obtained. In this scheme, user data is LDPC-encoded and written such that every codeword spans two tracks as opposed to one track as in conventional PMR.