Multiple UAVs for Joint Charging, Data Collection and Data Dissemination in Wireless Powered Sensor Networks

Multi-UAV-aided WPSNs (Multi Unmanned Aerial Vehicle aided Wireless Powered Sensor Networks) are promising for the emerging IoT (Internet of Things) applications. In the literature, one UAV is commonly adopted for one WPSN and it wirelessly charges the sensor nodes and collects their data. In this paper, we address two new issues in multi-UAV-aided WPSNs. First, we adopt multiple UAVs for a WPSN in order to support many sensor nodes over a large service area. With multiple UAVs, it is necessary to optimize the locations of the UAVs and the UAV-to-node association. Second, we utilize the UAVs for three joint functions: (i) wirelessly charging the sensor nodes, (ii) data collection from the sensor nodes, and (iii) data dissemination to the sensor nodes. We formulate an optimization problem to address the above two new issues, where the objective is to maximize the throughput. We prove that this problem is NP-hard and design a heuristic algorithm to tackle it. This algorithm iteratively executes two inter-dependent operations. The first operation optimizes the UAV-to-node association via load balancing among the UAVs, reducing the data transmission time. The second operation optimizes the UAV locations via Particle Swarm Optimization, reducing the charging time. The simulation results show that: (i) when more UAVs are used, the throughput is significantly increased, and (ii) the proposed algorithm efficiently determines the locations of the UAVs and the UAV-to-node association for joint charging, data collection and data dissemination.