Performance evaluation of 802.11ah Viterbi decoder for IoT applications

This research is our first step on the purpose of developing low-complex Viterbi decoder for IoT applications. We evaluate how the values of Viterbi decoder´s parameters such as trace back length (L), input data bit-width (D), and LLR truncated value (E), affects to BER and PER of a communication system. The IEEE 802.11ah simulator is used with AWGN channel and BPSK modulation. Our simulation results show that both BER and PER performance are improved if L value increased. However, if L is large enough, i.e., L ≥ 60, the performance improvement becomes insignificant. In addition, both BER and PER performance are continuously improved if D value increases from 1 to 4 bits. The best improvement of both BER performance (i.e., 1.8dB) and PER performance (i.e., 1.5dB) can be seen when D increases from 2 to 3 bits. Thus D = 3 is proposed for Viterbi decoder´s hardware development. When D ≥ 4 both BER and PER performance are almost unimproved although D continues to increase. Finally, our research shows that truncating the LLR value to E = 1.75 helps the Viterbi decoder achieves the best BER and PER performance in case D = 3 bits. Base on these research results, we come to the conclude of using 20 ≤ L ≤ 40, D = 3 bits, and E ≈ 1.75 for future development of low complex Viterbi decoder circuit for IoT applications. Furthermore, in this paper we introduce some mathematics equations for simplifying the Viterbi decoder process.