Showing papers by "Jack K. Wolf published in 1999"

Turbo decoding for PR4: parallel versus serial concatenation

Abstract: Recent work on the application of turbo decoding techniques to partial response class 4 (PR4) channels has focused on parallel concatenation systems that require three a posteriori (APP) detectors. A simplified serial concatenation system is presented that uses as its outer code a single convolutional code and as its inner code the partial response channel. An extension of this serial concatenation system is also presented that combines a second code with the channel, forming a more powerful inner code. Both proposed systems require only two APP detectors, offering significant savings in complexity and computation time. These serial concatenation systems are shown to perform as well as the more complicated parallel concatenation systems, offering substantial gains over uncoded systems. Additionally, the effect of precoding is investigated. Simulation results comparing the parallel and serial concatenation systems are also presented.

Turbo decoding for partial response channels with colored noise

Abstract: Recent work on the application of turbo decoding techniques to partial response channels has focused on additive white Gaussian noise channel models. Simulations using these ideal partial response channel models show gains exceeding 5 dB over uncoded systems at bit error rates of 10/sup -5/. Since the APP detectors of the turbo decoder assume uncorrelated Gaussian noise, the performance on more realistic channel models, using correlated noise, was unknown. In this work, we replace the white noise partial response channel model with the more realistic equalized Lorentzian channel model. Simulation results of the turbo decoding system with both channel models will be presented.

Iterative decoding for concatenated error correction coding in PRML channel systems

Abstract: A new iterative decoding scheme was developed for the cyclic redundancy check error correction code (CRCC), a concatenated error correction coding system. This simple iterative decoder achieves efficient cooperation between an outer Reed-Solomon error correction code (RS-ECC) decodes and a PRML trellis-detector. By using "error-free" decoded bit-information feedback from the outer RS-ECC decoder, the iterative scheme employs "state pinning" in the ML trellis-detector. This enables long error-events in the ML-decoded data to be corrected efficiently without adding extra coding redundancy and specific decoding complexity. The iterative scheme improves the correction capability of the outer RS-ECC coding by making use of a CRCC coding for specific correcting short error-events. Simulation shows that the iterative scheme achieves significant improvement in RS-ECC error-rate performance for a rate 16/17 quasi-MTR-coded Modified E/sup 2/PRML (ME/sup 2/PRML) channel in conjunction with CRCC coding.

Implementation and analysis of nonlinear effects in the microtrack model

Abstract: The implementation of nonlinear write effects in the microtrack model are investigated. Two different models for nonlinear transition shift are compared. Several methods for analyzing the output from the microtrack model are presented. Results from the microtrack model are also compared to results from spinstand tests. Agreement is dependent on the settings of the parameters in the model.

Efficient coding for a two-dimensional runlength-limited constraint

Abstract: Runlength-limited (d,k) constraints and codes are widely used in digital data recording and transmission applications. Generalizations of runlength constraints to two dimension are of potential interest in page-oriented information storage systems. However, in contrast to the one-dimensional case, little is known about the information-theoretic properties of two-dimensional constraints or the design of practical, efficient codes for them. In this paper, we consider coding schemes that map unconstrained binary sequences into two- dimensional, runlength-limited (d, (infinity) ) constrained binary arrays, in which 1's are followed by at least d 0's in both the horizontal and vertical dimensions. We review the derivation of a lower bound on the capacity of two-dimensional (d, (infinity) ) constraints, for d greater than or equal to 1, obtained by bounding the average information rate of a variable-to-fixed rate encoding scheme, based upon a 'bit- stuffing' technique. For the special case of the two- dimensional (1, (infinity) ) constraint, upper and lower bounds on the capacity that are very close to being tight are known. For this constraint, we determine the exact average information rate of the bit-stuffing encoder, which turns out to be within 1% of the capacity of the constraint. We then present a fixed- rate, row-by-row encoding scheme for the two-dimensional (1, (infinity) ) constraint, somewhat akin to permutation coding, in which the rows of the code arrays represent 'typical' rows for the constraint. It is shown that, for sufficiently long rows, the rate of this encoding technique can almost achieve that of the variable-rate, bit-stuffing scheme.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Turbo decoding for partial response channels with media noise

Abstract: Previous work on the application of turbo decoding techniques to partial response channels has focused on additive white Gaussian noise channel models. Simulations using these ideal partial response channel models show gains exceeding 5 dB over uncoded systems at bit error rates of 10/sup -5/. Since the APP detectors of the turbo decoder assume uncorrelated Gaussian noise, the performance on more realistic channel models, using correlated and media-dependent noise, was unknown. In this work, we replace the white noise partial response channel model with more realistic channel models. First, the effects of colored noise are investigated with an equalized Lorentzian channel model. Then, media noise is added by incorporating the microtrack model into the system. Simulation results of the turbo decoding system with the various channel models are presented. Additionally, since the use of an outer Reed-Solomon code is anticipated in an actual system, the burst statistics at the error floor are investigated.