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

The write-margin of the iterative decoding systems for the binary and non-binary low-density parity-check (LDPC) codes are studied in the magnetic recording system using a bit-patterned medium (BPM) R/W channel with write-errors caused by the write-head field gradient, the media switching field distribution (SFD), the magnetization fields from adjacent islands, and the island position deviation. The performances of iterative decoding systems using the binary and non-binary LDPC codes are evaluated by computer simulation at an areal recording density of 2 Tb/inch². The results show that the non-binary LDPC coding and iterative decoding system improves the write-margin compared with the binary LDPC system. Furthermore 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.