Two-dimensional soft output Viterbi algorithm with noise filter for patterned media storage

Abstract

We introduce a two-dimensional (2D) soft output Viterbi algorithm (SOVA) using two 1D SOVAs, which apply two noise filters corresponding to horizontal and vertical directions, respectively, for patterned media storage. Patterned media storage has 2D intersymbol interference (ISI), which includes ISI from neighboring symbols and intertrack interference from adjacent tracks, since there is a small space between adjacent tracks and neighborhood symbols. Noise filter replaces colored noise with white noise. As a result, the noise filter can reduce the noise power, so that performance can be improved. As shown in the simulation results, when there is no off-track, the 2D SOVA using a noise filter is approximately 0.4 dB better than not using a noise filter at a 10−6 bit error rate; when there is 20% off-track, it has about a 1 dB gain.