A comparison between the M-algorithm and the list Viterbi algorithm

In this paper we compare the performances of the M-algorithm (MA) and the list Viterbi algorithm (LVA) for a concatenated coding scheme with outer cyclic redundancy code (CRC) and inner convolutional code. Even though the Viterbi algorithm (VA) performs the optimum decoding for convolutional codes, it is sub-optimum for the concatenated system. The LVA provides an ordered list of decoded bit sequences by embedding limited list search in its trellis structure. On the contrary, the MA is a list-based algorithm which can be viewed as a constrained tree search decoder. Our results show that for the considered concatenated system, list-based algorithm outperforms trellis-based algorithm for equivalent complexity. A set of simulation results are presented comparing these algorithms for different constraint lengths, code rates and channel conditions.