Energy-Efficient UAV-Assisted WSN: 3D Trajectory Design for Joint Positioning and Data Collection

Unmanned aerial vehicles (UAVs), serving as aerial base stations (BSs), are able to provide not only the communication services for data collection from sensor nodes (SNs), but also the sensing capabilities for localizing SNs in wireless sensor networks (WSNs). In this article, we propose a novel UAV-assisted WSN framework with integrated sensing and communications (ISAC) functionalities, in which a UAV platform acts as both a mobile data collector and an aerial anchor node to assist WSN in reducing SNs' energy consumption and enhancing SNs' 3D positioning accuracy considering SNs' distributed altitudes. The objective is to minimize the energy consumption across all SNs by jointly optimizing the UAV's 3D trajectory and UAV task allocation schedule over time, while meeting the required SNs' 3D positioning accuracy. This task is formulated as a mixed-integer non-convex optimization problem, and an efficient differential evolution (DE) based iterative optimization method is proposed to solve it. Numerical results indicate that the proposed framework and optimization method achieve significant improvements in both energy-efficient data collection and highaccuracy 3D positioning, comparing to that of UAV 2D trajectory designs or conventional terrestrial sensor networks.