Concatenated coding for binary partial-response channels

Concatenation of outer conventional rate-k_c/n_c binary convolutional coding with inner rate-k_t/n_t special trellis coding for the binary 1-D dicode partial-response channel is investigated. In the scheme considered, code sequences generated by the outer convolutional encoder are time-interleaved prior to trellis encoding. Decoding for the outer convolutional code takes into account the reliability of individual code symbols provided by the inner trellis-decoding stage. The construction of the inner trellis code is based on the partitioning of a set of sequences of noiseless channel-output signals into subsets which are assigned to the branches of a combined encoder and channel trellis. A class of trellis codes is obtained that guarantee a limited number of consecutive zeros at the channel output and allow for a computationally efficient estimation of the reliability of the decoded symbols. It is shown that substantial coding gains can be achieved by this method as compared to the maximum-likelihood sequence detection of uncoded dicode signals