A novel split soft-decision equalizer (SSE) with near-optimum performance is proposed for wireless multipath channels with large delay spread. The concept of SSE is significantly different from the traditional notions of the Viterbi algorithm and decision-feedback equalizer. Instead of dealing with received sequence as a combined sequence, it splits the received sequence into its constituent paths. Using an iterative soft-decision algorithm, reliability of the soft decisions on each decomposed element is improved iteratively. The major advantage of SSE is the independence of computation complexity on channel time dispersion. Joint design of SSE with a soft-decision decoder is also considered in this paper. Performance analysis and simulation results show that performance of the proposed algorithm comes very close to that of the logarithmic maximum a posteriori decoder.

A new hybrid automatic repeat-request (ARQ) scheme that uses supplementary trellis codes for retransmission is described. In this scheme, supplementary codes are designed to compensate for the squared free distance (d/sub free//sup 2/) of the trellis code used for the previous transmission. Differently encoded codewords are combined and decoded by the same Viterbi decoder at the receiver. This scheme provides improved (d/sub free//sup 2/) upon retransmission compared with that provided by the conventional trellis coded hybrid-ARQ scheme where the same coding scheme is used for all transmissions.