Write-margin evaluation of LDPC coding and iterative decoding system in BPM R/W channel with write-errors

The magnetic recording system using a bit-patterned medium (BPM) has serious problems such as the need of the precise write-synchronization to correctly write the recording sequence on each intended island and the write-errors caused by the insufficient write field gradient, the medium switching field distribution (SFD), the demagnetization fields from adjacent islands, and the island position variation. In this paper, the influences of the SFD and the demagnetization fields from adjacent islands on the write-margin of the low-density parity-check (LDPC) coding and iterative decoding system is studied in the BPM R/W channel with write-errors at an areal recording density of 2 Tbit/inch². It is clarified that in order to obtain the sufficient write-margin, it is important to suppress the influence of the demagnetization fields from adjacent islands.