Error Rate Performance of Turbo Coded Partial Response Systems for Digital Magnetic Recording Channels

Hidetoshi SAITO  Masaichi TAKAI  Yoshihiro OKAMOTO  Hisashi OSAWA  

IEICE TRANSACTIONS on Electronics   Vol.E82-C   No.12   pp.2218-2226
Publication Date: 1999/12/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Information Storage Technologies for the 21st Century)
digital magnetic recording,  partial response,  turbo coding,  MAP decoding,  partial erasure,  

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In various digital wireless communication systems, it is known that turbo coding provides an error rate performance within a few tenths of a dB of the theoretical Shannon limit. The error correcting capability of turbo coding is attractive for a recording code in a digital magnetic recording system. The performance of a partial response maximum-likelihood (PRML) system with any recording code is degraded by many undesirable factors such as linear and nonlinear distortions. For improving the performance of the PRML system, it is useful to adopt a high-order PRML system or high rate code in general. In this paper, the two-track recording system using turbo coding which can increase the coding rate over 1 and improve the performance is proposed. Turbo-coding provides a near-ML performance by the suboptimum symbol-by-symbol maximum a posteriori probability (MAP) decoding algorithm. Our proposed turbo-coded class 4 partial response (PR4) systems use the rate 4/6, 8/10 and 16/18 turbo codes for high-density two-track digital magnetic recording. The error rate performance is obtained by computer simulation, taking account of the partial erasure which is a prominent nonlinear distortion in high-density recording. As a result, the proposed systems are hardly affected by partial erasure and maintains good performance compared with the conventional NRZ coded PR4ML system.