Abstract: LoRa technology is widely used in agricultural Internet of Things. When the network scale is large, the standard LoRaWAN protocol can improve the SF to increase the communication distance. However, due to the co-SF and inter-SF interference, LoRaWAN's node density is limited, so it is not suitable for large-scale and high-density deployment scenarios. To meet the requirements of the above deployment scenarios, the multi-hop routing scheme and the SF allocation method are combined to optimize the LoRa network, which improves the node capacity and reliability of the network. Simulation results show that, the proposed method can achieve more than 80% Packet Delivery Rate (PDR) in LoRa network with more than 10 000 nodes, which significantly improves the reliability of LoRa networks in large-scale and high-density scenarios.

Key words: LoRa, spreading factor, high density, multi-hop network, packet delivery rate (PDR)