2-D Write/Read Channel Model for Bit-Patterned Media Recording With Large Media Noise

Abstract

A 2-D write/read channel model, which can accurately capture the media, writer, and reader characteristics, is proposed and investigated for very-high-density bit-patterned media recording (BPMR) system with large media noise. For the write process, a 2-D data-dependent write channel combined with a micromagnetic model of the writer is investigated for BPMR. In order to better understand the proposed channel model, several 2-D patterns are investigated, and the corresponding write failure events are studied. It is observed that the write error rates (WERs) are different for different 2-D patterns due to the 2-D data-dependent nature of the write-in errors, even though the write failure rates are the same for these different 2-D patterns. For the readback process, a read channel, including media noise, is combined with the write channel, and the bit error rates (BERs) are studied for various 2-D patterns as a function of media jitter and write clock phase drift. It is observed that the 2-D pattern corresponding to four identical bits in a square pattern provides the best performance at a target BER of $10^{\mathrm {-2}}$ , because it can provide adequate tolerance to media noise and interference in down-track and cross-track (CT) directions. The difference between the WER and the BER after readback is studied for various 2-D patterns, and the pattern corresponding to 4 bits with transitions in the CT direction is found to exhibit the largest difference among the studied patterns due to the fact that inter-track interference is more severe than the inter-symbol interference. These results motivate possible inclusion of 2-D modulation codes in BPMR channel to avoid certain bit patterns.