A new method for Viterbi decoder simulation using importance sampling

Each simulation run simulates a single error event-that is, a subsequence of incorrect trellis branching decisions-and importance sampling is used to emphasize important nontrivial error events. The fundamental principles of the error event simulation method in conjunction with importance sampling are reviewed. The importance sampling background for coded communications systems is discussed in the context of block codes, because it is easier to present the fundamentals of importance sampling without the additional complexities of Viterbi decoding. The details of the error event simulation method for Viterbi decoders and numerical examples that demonstrate this method are presented. These numerical examples involve both hard and soft decision decoding for the ideal additive Gaussian noise channel. The technique is shown to provide markedly improved efficiency