Modified adaptive Viterbi algorithm for convolutional codes decoding

This paper introduces an efficient modification to one of the most successful complexity reduction techniques of the Viterbi decoding algorithm; the adaptive Viterbi algorithm. Although the use of the adaptive algorithm made it practically visible to use convolutional codes with large constraint lengths, the decoding complexity reduction at lower signal-to-noise ratios is not as good as that at higher signal-to-noise ratios. In this work we have modified the elimination rule for the adaptive Viterbi algorithm based on minimum free distance threshold. The proposed algorithm can preserve the same error performance as the adaptive Viterbi algorithm while requiring a substantially smaller average number of computations at wider range of signal-to-noise ratios.