An optimal circular Viterbi decoder for the bounded distance criterion

Abstract

We propose a Viterbi-type decoder for tailbiting trellis codes that works by traversing the tailbiting circle somewhat more than once. The traversal is the least possible for any bounded distance Viterbi decoder. Procedures are given that compute this minimum. Unlike previous decoders of the type, the new scheme does not suffer limit cycles or from pseudocodewords. The bit-error rate is compared to that of Bahl-Cocke-Jelinek-Raviv and maximum-likelihood decoding.