Group codes generated by finite reflection groups

Slepian-type group codes generated by finite Coxeter groups are considered. The resulting class of group codes is a generalization of the well-known permutation modulation codes of Slepian (1965), it is shown that a restricted initial-point problem for these codes has a canonical solution that can easily be computed. This allows one to enumerate all optimal group codes in this restricted sense and essentially solves the initial-point problem for all finite reflection groups. Formulas for the cardinality and the minimum distance of such codes are given. The new optimal group codes from exceptional reflection groups that are obtained achieve high rates and have excellent distance properties. The decoding regions for maximum-likelihood (ML) decoding are explicitly characterized and an efficient ML-decoding algorithm is presented. This algorithm relies on an extension of Slepian's decoding of permutation modulation and has similar low complexity,.