Abstract : Among variant low-power wide area networks (LPWAN),LoRa is one of the most promising and is extensively deployedworldwide because of its satisfactory performance and relativelylow cost. In the foreseen future, various internet of things (IoT)applications are required to sustain connectivity for massive enddevices.Massive connectivity challenges the LoRaWAN networkbased on ALOHA medium access control (MAC) protocol due tosevere collisions under high traffic loads. To solve this problem,we first dissect the principles and characteristics of LoRa physicallayer. And it suggests that the capture effect among the signalswith the same spreading factor (SF) and different SFs can beadequately leveraged to improve performance. Based on the captureeffect, we develop a new receiver structure that enables thesuperposed LoRa signals with different odd/even SFs to be demodulatedsimultaneously. A suitable novel MAC protocol exploitingsuch concurrent transmissions is further presented. Simulationsverify that, through utilizing the capture effect, the proposed protocolcan partly tackle the collisions due to numerous access attempts,which results in enhancing the throughput compared toLoRaWAN. These results show that the proposed scheme is compliantwith the requirement of IoT applications with massive connectivity.
Index terms : Capture effect, LoRa, low-power wide area networks (LPWAN), massive connectivity, medium access control (MAC).