Soft output Viterbi algorithm (SOVA) for non-binary turbo codes

An optimal MAP-equivalent SOVA decoding algorithm and its simplified suboptimal algorithm for non-binary codes are proposed. The implementation of its suboptimal algorithm is simpler, while its performance is very close to the optimal Log-MAP algorithm. The proposed SOVA can be used as a decoder for turbo trellis coded modulation (TTCM). It is concluded that the proposed SOVA performs very close to the Log-MAP algorithm for both the TTCM and binary turbo codes, and its performance is better than the conventional SOVA.