Optimal code rates for concatenated codes on a PR4-equalized magnetic recording channel

At some nominal recording density, the read signal In digital magnetic reco rding resembles a Class IV partial response (PR4) signal and, hence, may be equalized to the PR4 shape with relatively little noise enhancement. When coding is added, for a fixed user density, the recording density must incre ase as a result of coding overhead, and the read signal will resemble PR4 t o a lesser extent. Equalization-to PR4 in this-case will-produce excessive noise enhancement. Thus, coding overhead (or rate) must be selected for opt imum tradeoff between code strength and noise en hancement. Toward this end , we provide results for high-rate concatenated codes, assuming a Lorentzia n recording Channel model. In addition to examining optimal code rates) me compare parallel and serial concatenated code performance on the PR4 channe l.