ON CODING AND DECODING FOR HIGH-ORDER PARTIAL-RESPONSE SYSTEMS

High-data-rate signal processing for hard disk drives is discussed. A recording channel is equalized as a partial response (PR) (1+D)(1-D-3) , where D is a delay operator. Furthermore, 1/(1+D) pre-coding scheme is used, and the resulting response is given as (1-D-3), which achieve s three-bit interleaving. The working speed of each Viterbi detector i n interleaving PR channels is reduced to one third of the original bit -frequency. The performance of the reduced two-state Viterbi detector in the interleaving PR channel is compared with the conventional two-s tate Viterbi detector of the PR4 system. As a result, the proposed sys tem improves the signal-to-noise ratio by about 3.0 dB compared with t he baseline PR4 maximum likelihood system. Finally, it is shown that t he Error Coding (ECC) scheme for the interleaving needs a reversed hie rarchy of ECC and channel coding.