Simplified EPRML methods based on selective ACS for high-density magnetic recording channels

S-EPRML (simplified extended partial response maximum likehood) methods appropriate for signal processing with simple hardware complexity on high-density magnetic recording channels are proposed. The basic idea is “selective ACS”, that is, to selectively apply the ACS (add, compare, and select) operation only for the states in the EPR4 channel trellis, that are substantially operative in the sense of the MLSE (maximum likelihood sequence estimation). Our methods can significantly reduce the effective number of states for ACS to two or less if (1,7) RLL coding is used. Computer simulated results show that the proposed methods maintain almost the same error-rate performance as the conventional EPRML method