Turbo codes cascaded with high-rate block codes for (O,Κ)-constrained channels

摘要

We consider several issues in the analysis and design of turboncoded systems for (O, Κ) input-constrained channels. Thesenconstraints commonly arise in magnetic recording channels. This systemnis characterized by a high-rate turbo code driving a high-rate (n-1)/n,nsmall-length (O, Κ) block code. We discuss the properties of then(O, Κ) code that affect its performance on both an additive whitenGaussian noise (AWGN) and a precoded dicode channel. We address soft-innsoft-out (SISO) decoding of linear and nonlinear (O, Κ) codes andnshow that good (O, Κ) codes exist even when dmin=1. Fornthe (O, Κ) constrained AWGN channel, we present several raten(n-1)/n block codes that optimally tradeoff bit-error-rate performancenwith Κ. For the precoded dicode channel, we show that thensystematic (O, n-1) modulation codes are superior to most other raten(n-1)/n block codes in terms of error-rate performance, and theirnattractiveness is increased by the fact that they do not contribute anynsignificant complexity to the overall system