The principal research areas of this project (for Lancaster University) are:(I) investigation of optimum decoder synthesis for Sequence-Segment Keying (SSK), taking into account diversity;(ii) investigation of optimum error control schemes for use in SSK-type systems;(iii) investigation of variable-significance SSK, adaptive in response to nature of source information.Progress:To date (Lancaster):The optimum decoder synthesis is a balance against performance and complexity (both time and space complexity). This balance has been investigated by comparing the relative decoder complexities of hard-decision decoders; Euclidean, Berlekamp-Massey and High-Speed Step-by-Step decoders have been implemented in C++. The complexity evaluation was based upon the number of Galois field operations performed, with each operation weighted according to the projected execution time on a DSP. The decoders were also compared against a minimum-weight decoder under the same criteria. It was found that while High-Speed Step-by-step is an improvement over conventional step-by-step decoding Euclidean and Berlekamp are less complex (and still retain (hard-decision) maximum likelihood decoding). Minimum-weight decoding is the least complex but is not maximum-likelihood. A soft-maximum-likelihood trellis decoder has been implemented in C++. Currently work is progressing to extend this to the decoding of Reed-Solomon codes, allowing a comparison of decoder complexity against the decoders already discussed.