Two-Dimensional Soft Output Viterbi Algorithm With Dual Equalizers for Bit-Patterned Media

This study proposes a two-dimensional (2D) detection method using partial response maximum likelihood (PRML) for bit-patterned media (BPM) storage. Because the readback signals are deteriorated by 2D channel effect, that is, intersymbol interference along the track direction and intertrack interference across the track direction, it is necessary to use “2D” PRML in order to improve the bit error rate (BER) performance. The 2D PRML in the proposed method is based on the 2D soft output Viterbi algorithm (SOVA), which is composed of two one-dimensional SOVAs. In addition, we propose a 2D SOVA for a 2D partial response (PR) target using dual equalizers: one estimates the correlated signal (output data of the PR target), used as the main information with encoding rule, and the other estimates the binary signal (binary data recorded on BPM), used as extrinsic information on the other direction's neighboring bits. The simulation results show that the proposed method improves the BER performance at a low computational complexity.