UAV-Aided Emergency Environmental Monitoring in Infrastructure-Less Areas: LoRa Mesh Networking Approach

Rapid acquisition of environmental parameters of emergency sites is crucial for emergency response. However, in areas where public ground networks do not provide sufficient coverage or are destroyed by disasters, the rapid backhaul of monitoring data from emergency sites is difficult. Due to the urgent demand for data collection in such areas, we propose an unmanned aerial vehicle (UAV)-aided emergency environmental monitoring system using a LoRa mesh networking approach, which can quickly build a large range of wireless communication networks suitable for small data transmission. First, we designed a LoRa-based mesh network protocol by using a custom slotted ALOHA medium access mechanism. Second, we designed and implemented a custom software and hardware platform of the monitoring system. The system adopts a communication mode, including multiple sensor nodes (SNs), multiple relay nodes (RNs), a gateway (GW), and a network server. Finally, we demonstrated the performance of the protocol and the system by in-lab and outdoor tests. The results show that when data rate is 0.293 kb/s, the line-of-sight 1-hop transmission distance is more than 10 km, and the 1-hop transmission delay is less than 6 s; the end-to-end delay has an upper bound, which can meet the real-time requirement of emergency response; the least upper bound of throughput per slot of our mesh protocol is much higher than that of LoRaWAN. Evaluation results also demonstrate the network robustness to environmental changes.