Uniformly efficient trellises for self-dual codes
Houshou Chen, J.T. Coffey · 2002
Uniformly efficient trellis decoders are known for very few codes, and no general method is known that can decide whether such a decoder exists. It is shown that this question is substantially simplified in the case of self-dual codes, when certain subcodes meet the Griesmer bound with equality. Furthermore, in many cases the result makes it possible to count the number of uniformly efficient permutations. In some cases the existence and number of uniformly efficient trellises may be deduced directly from the parameters of the code. Among the codes that meet the criterion are the [24,12,8] Golay code, for which the number of uniformly efficient permutations is derived, four of the [32,16,8] doubly even codes, and the [48,24,12] quadratic residue code, for which a lower bound on the number of uniformly efficient permutations is derived.