Application of the Berrou SOVA algorithm in decoding of a turbo code

We present a turbo decoder that is based on a low complexity soft output Viterbi algorithm (SOVA) introduced by Claude Berrou et al. in ICC'93. It is conceptually different from the conventional turbo decoders, where the iteration is based on the a posteriori probabilities (APP). The constituent Berrou SOVA decoders make the maximum likelihood (ML) decision on the correct path in the trellis, and they have lots of similarities with a conventional hard decision Viterbi decoder—their complexity is double that of the Viterbi due to extraction of the soft output. The iterative Berrou SOVA decoder is able to achieve a relatively high speed: the constituent decoders can work at the same pace as their conventional Viterbi counterparts, and no back tracing is needed. The performance is competitive with the traditional decoding algorithms. In comparison with Max‐Log‐MAP, we have attained a slightly better performance.