Reduced-Complexity Decoding of LDPC Codes for Generalized Partial Response Channels

The performance of low-density parity-check (LDPC) codes serially concatenated with generalized partial response channels is investigated. Various soft-input/soft-output detection schemes suitable for use in iterative detection/decoding systems are described. A low-complexity near-optimal detection algorithm that incorporates soft-input reliability information and generates soft-output reliability information is presented. A reduced-complexity algorithm for decoding LDPC codes is described. Simulation results on the performance of high-rate LDPC codes on generalized PR channels at various recording densities are presented. These results indicate that a judicious selection of the inner detector target polynomial and the choice of a good LDPC code are important in optimizing the performance of the overall recording system. Furthermore, the results also show that iterative detection/decoding schemes using LDPC codes can outperform hard-decision decoding of Reed-Solomon codes by over 2 dB at a sector error rate of 10^-3.

Keywords: Iterative detection/decoding, NPML, LDPC codes, dual-max algorithm, sum-product decoding.