Comparing List Viterbi Algorithms with and without tail bits

In this paper we evaluate the impact of tail bits on the performance of list Viterbi algorithms (LVA). The LVA provides an ordered list of decoded bit sequences. The outer cyclic redundancy check (CRC) block code, concatenated with the convolutional code, is used to select the output sequence. For the conventional Viterbi algorithm (VA), tail-biting outperforms tail bit-aided decoder with additional complexity. However, for the concatenated system, tail-biting algorithm applied to the LVA does not perform as well. Since tail bits incur rate loss, we propose an alternative algorithm where the tail bit-aided LVA with puncturing is employed. The tail-punctured LVA, while retaining the original code rate, provides good performance with reduced complexity. A set of simulation results are presented comparing these algorithms for different constraint lengths, code rates and channel conditions.