Detection-Decoding on BPMR Channels With Written-In Error Correction and ITI Mitigation

Written-in errors and inter-track interference (ITI) are recognized as key and unique performance-limiting factors in bit-patterned media recording (BPMR). Hence, in this paper, we consider data recovery on a BPMR channel model consisting of a write channel producing data-dependent written-in errors followed by a partial response read channel with the addition of ITI. The Davey-MacKay (DM) serial concatenated coding scheme is employed to handle the written-in errors while multi-track (MT) detection and 2D-equalization are used to mitigate the inter-symbol interference (ISI) and ITI. Three detection-inner-decoding schemes are proposed to work with an outer decoder to recover the data on the BPMR channel, namely the BCJR-binary-input-inner-decoder (BCJR-BIID) algorithm, the joint detection-inner-decoder (JDD) algorithm and the BCJR-soft-input-inner-decoder (BCJR-SIID) algorithm. Media configurations leading to areal densities of 2.64 Tb/in² and 4 Tb/in² with comparable ISI but significantly higher ITI in the latter case are considered. Computer simulations show that at low to moderate (resp., high) signal-to-noise ratios (SNRs), BCJR-SIID (resp., BCJR-BIID) provides good performance-complexity trade-offs. It is also shown that increasing the areal density from 2.64 Tb/in² to 4 Tb/in² while the written-in error rates remain fixed, does not significantly affect error performance on the BPMR channel. Rather, it is the burst errors preceding and following an insertion or deletion that has a significant impact on performance.