Based on the Lorentzian model of the magnetic recording channel the effect of increasing linear density is investigated. It is observed that for a fixed turbo equalization scheme, which consists of a 16-state NPML detector and a decoder for a fixed LDPC code, the gap between the performance of the turbo equalization scheme and the Shamai-Laroia bound of the channel increases substantially with increasing linear density. Two complementary methods for reducing this gap to capacity at high linear densities are considered. First, without increasing the complexity, noticeable gains can be obtained by using a binary 1/(1+D) precoder for the partial response channel. Second, selecting a longer partial response target provides substantial gains at high densities. Moreover, when both methods are applied, the two individual gains add up.
By: Thomas Mittelholzer and Evangelos Eleftheriou
Published in: RZ3462 in 2002
LIMITED DISTRIBUTION NOTICE:
This Research Report is available. This report has been submitted for publication outside of IBM and will probably be copyrighted if accepted for publication. It has been issued as a Research Report for early dissemination of its contents. In view of the transfer of copyright to the outside publisher, its distribution outside of IBM prior to publication should be limited to peer communications and specific requests. After outside publication, requests should be filled only by reprints or legally obtained copies of the article (e.g., payment of royalties). I have read and understand this notice and am a member of the scientific community outside or inside of IBM seeking a single copy only.
Questions about this service can be mailed to reports@us.ibm.com .