A novel MAC protocol exploiting concurrent transmissions for massive LoRa connectivity

摘要

Among variant low-power wide area networks (LPWAN), LoRa is one of the most promising and is extensively deployed worldwide because of its satisfactory performance and relatively low cost. In the foreseen future, various internet of things (IoT) applications are required to sustain connectivity for massive end-devices. Massive connectivity challenges the LoRaWAN network based on ALOHA medium access control (MAC) protocol due to severe collisions under high traffic loads. To solve this problem, we first dissect the principles and characteristics of LoRa physical layer. And it suggests that the capture effect among the signals with the same spreading factor (SF) and different SFs can be adequately leveraged to improve performance. Based on the capture effect, we develop a new receiver structure that enables the superposed LoRa signals with different odd/even SFs to be demodulated simultaneously. A suitable novel MAC protocol exploiting such concurrent transmissions is further presented. Simulations verify that, through utilizing the capture effect, the proposed protocol can partly tackle the collisions due to numerous access attempts, which results in enhancing the throughput compared to LoRaWAN. These results show that the proposed scheme is compliant with the requirement of IoT applications with massive connectivity.