Throughput Enhancement in UAV-aided Wireless Sensor Networks via Wake-Up Radio Technology and Priority-based MAC Scheme

UAV-aided Wireless Sensor Networks (WSNs) constitute an energy- and cost-effective solution for the deployment of large-scale IoT monitoring systems. At the same time, the integration of UAVs into IoT scenarios poses some practical challenges which are far to be addressed, like the synchronization issue (how can the Wireless Ground Sensors (WGSs) be aware of the presence of the UAV?) and the channel contention in high-dense scenarios (how can the WGSs cope with the limited transmission opportunity?). In this paper, we address both the issues above by proposing a novel Energy Load Aware Sensor To aIr Communication (ELASTIC) platform, supporting the deployment of scalable and energy-efficient UAV-aided WSNs. The proposal includes two main components, working in synergy at the PHY and MAC layers. First, the paper describes the design and implementation of Active Wake-up Radio mechanisms through which the WGSs can be notified of the UAV's presence and hence of the transmission opportunity; the proposed architecture supports two operative modes (Switch and Low-Power) that can be properly orchestrated so that the energy consumption of the WGSs in standby phase is minimized. Second, since multiple WGSs can be activated from a wake-up signal and access the channel at the same time, a novel priority-based MAC scheme has been designed: the proposed solution performs distributed contention control among the WGSs, by taking into account the length of the transmission opportunity for each WGS and the actual channel load. The simulation results demonstrate that the proposed ELASTIC MAC protocol guarantees a +50% throughput improvement when compared to the legacy CSMA/CA MAC in high-dense WSNs, and show its ability to adapt to different traffic loads and UAV speeds.