LDPC decoder with modified LLR for bit patterned media with write errors

Write-in error is a crucial issue that needs to be tackled in bit patterned media (BPM) recording. Previous works apply the low-density parity-check (LDPC) codes to improve the system performance and the write margin. However, LDPC codes are not designed for the write error channel (WEC). Therefore, the log-likelihood ratio (LLR) is modified at the LDPC decoder by incorporating the information write error probability (p) for the performance improvement. In practice, such probability is not precisely known, therefore, in this work, we investigate the effects of the mismatch of expected write error probability and the actual one in the BPM system. The results show that the performance of LDPC decoding is worse when p mismatches with the write error probability of the WEC.