A circular MAP decoder for error-correcting trellis codes that employ tail biting produces soft-decision outputs provides an estimate of the probabilities of the states in the first stage of the trellis, which probabilities replace the a priori knowledge of the starting state in a conventional...http://www.google.de/patents/US5721746?utm_source=gb-gplus-sharePatent US5721746 - Optimal soft-output decoder for tail-biting trellis codes
