Concatenated Coding for Binary Partial-Response Channels

Concatenation of outer conventional rate-k/sub c//n/sub c/c binary convolutional coding with inner rate-k/n special trellis coding for binary partial-response 1-D channels is investigated. In the considered scheme, the code sequence generated by the convolutional code is 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 trellis code is designed to achieve large minimum Euclidean distance. The reliability of the decoded symbols is obtained in a computationally efficient way. The construction of the trellis code is based on the partitioning of a set of noiseless channel-output sequences into subsets which are assigned to the branches of a combined encoder and channel trellis. An algorithm for constructing the subsets of channel-output sequences is discussed. Trellis codes with various rates, minimum distances, and complexities are described and the performance achieved by concatenation with different convolutional codes is presented. It is shown that substantial coding gains can be achieved by this method as compared to the maximum-likelihood sequence detection of uncoded binary signals.