Improvements in SOVA-based decoding for turbo codes

In this paper, we propose two modifications to soft output Viterbi algorithm (SOVA) for turbo code decoding. One is to limit the reliability values to a small range to compensate for the defect brought by overestimating those values in the original SOVA. The other is to employ a new block interleaver to combat the tail effect of SOVA-based turbo code decoding. The simulation results show that the new SOVA with both modifications is able to obtain a similar result to that achieved by a maximum a posteriori (MAPI) algorithm with a random interleaver. In this paper, we also provide the results of the SOVA with the Battail´s updating rule and compare them to those of the SOVA with the updating rule proposed by Hagenauer