We consider maximum-likelihood decoder performance in additive white Gaussian noise for the serial concatenation of an outer code comprising multiple, independent odd-parity-check codes and an inner precoded dicode partial-response channel through a random interleaver. Using a technique proposed in Oberg and Siegel (1998, 2001) we derive an approximation of the average weight enumerator, assuming that code bit values within error events are independent, identically distributed, and equiprobable. We show that the union bound on word-error-rate based upon the approximate weight enumerator is actually an upper bound to that based upon the true average weight enumerator, for suitably large signal-to-noise ratios.

The performance of maximum-likelihood decoding of a serial concatenation comprising a high-rate block code, convolutional code, or a turbo code, a uniform interleaver, and a partial response channel with additive white Gaussian noise is addressed. The effect of a channel precoder on the system performance is also considered. Bit- and word-error rate estimates based upon properties of the average Euclidean distance spectrum of the coded partial response channel are derived. The estimates are compared to computer simulation results, and implications for system design are discussed.

The partial response channel can be viewed as a rate-1 encoder in which the output alphabet differs from the input alphabet. In serially concatenated coding schemes, the partial response channel can serve as the inner encoder. Previous work on the application of turbo decoding techniques to partial response channels has focused on using a parallel concatenation of convolutional encoders as the outer code and the partial response channel as the inner code. This system requires three a posteriori probability (APP) detectors-one matched to the channel and two matched to the constituent encoders. A simplified system is presented that uses as its outer code a single convolutional code and as its inner code the partial response channel. The simplified system requires only two APP detectors, offering significant savings in complexity and computation time. This single convolutional code system is shown to perform as well as the more complicated system, offering substantial gains over uncoded systems. Simulation results for three magnetic recording channel models are presented: a partial response channel with additive white Gaussian noise, an equalized Lorentzian channel model, and a media noise model called the microtrack model. Since the use of an outer Reed-Solomon code is anticipated in an actual system, the burst-error statistics are investigated. System performance with various interleaver designs and precoders is also investigated.

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.