Iterative Decoding for Digital Recording Systems

In many existing optical and magnetic digital recording systems, data is usually encoded by a cascade of several encoders, followed by a channel with IS1 (intersymbol interference). Conventional receivers follow a one-path approach, where an equalizer is followed by a cascade of appropriate decoders. We propose a backward compatible iterative receiver which uses generalized erasures. An AZD (ambiguity zone detection) detector labels unreliable symbols as erasures. These are then resolved in an iterative process by the equalizer and the decoders. The proposed decoding scheme can significantly improve the system performance. It is implementable with low decoding complexity, and introduces only a small decoding delay.