Adaptive Viterbi Decoding Algorithm for the Shortened (38,26) BCH Code Based on Trellis

Galileo search and rescue system (Galileo/SAR) adopts the shortened (38,26) BCH code in its physical layer protocol. In this paper, an adaptive Viterbi decoding algorithm (AVA) was proposed. The best trellis for the shortened (38,26) BCH code was first presented. In the AVA, a discarding threshold was designed on the basis of the Viterbi algorithm (VA), only retaining the most likely paths. The discarding threshold could vary with the different SNR and be adjusted adaptively to reduce the decoding complexity as much as possible, with almost the same error performance as the VA. Simulation results show that, the decoding complexity of the AVA reduces greatly compared with the VA, maintaining nearly the same error performance. Especially at high SNR, the decoding complexity decreases more obviously.