Concatenated code system design for storage channels

A number of papers have recently been published on the concatenation of an outer code with a partial response (PR) channel, where the outer code is a turbo code, a convolutional code, or a low-density parity-check code, This paper deals with the second case, assuming EPR4 and modified extended EPR4 (MEEPR4) partial response (PR) targets. The goals in this work include 1) t he joint optimization of interleaver and precoder for a fixed outer convolu tional code and PR target, 2) the choice of optimal code rate for both PR t argets assuming a Lorentzian model, and 3) an assessment of the performance of these codes in the presence of thermal asperities. We introduce mathema tical and algorithmic tools for accomplishing these goals and present simul ation results that support our approach, Among the positive results is the ability to lower the well-known error rate floor of these concatenated sche mes for arbitrary PR channels.