A concatenated coding technique for partial response channels

A new concatenated coding technique has been developed for high-order PRML channels, Its first key feature is a pre-error-correction-coding (pre-ECC) scheme comprising cyclic-redundancy-check ECC (CRCC) coding and simplified soft-output decoding, The CRCC coding, a very-low-redundancy inner-block EC C concatenated to the PRML channel, specifically corrects dominant short er ror-events in the ML-detector The soft-output decoding enhances the CRCC co ding capability through the list and soft-symbol output Viterbi-algorithm ( list-SOVA), A second key feature is an iterative decoding scheme to ensure efficient cooperation between an outer Reed-Solomon (RS) ECC and the ML-det ector, By using error-free decoded bit-information feedback from the outer RS-ECC decoder, the iterative scheme employs "state pinning" in the ML trel lis-detector, This enables long error-events remaining after the CRCC decod ing to be corrected efficiently without increasing the coding redundancy an d the decoding complexity, Complementary use of the iterative scheme for lo ng error-events and the CRCC decoding for dominant short error-events impro ves the total system error-rate performance, Simulation showed that the con catenated coding scheme could significantly improve the RS-ECC error-rate p erformance of a 16/17-rate quasi-MTR-coded (MEPRML)-P-2 channel when used i n conjunction with CRCC coding.