Joint Optimization of UAV Trajectory and Number of Reflecting Elements for UAV-Carried IRS-Assisted Data Collection in WSNs Under Hover Priority Scheme

Uncrewedaerial vehicle (UAV)-carried intelligent reflecting surfaces (U-IRSs) can be utilized to assist blocked communications between sensor nodes (SNs) and the fusion center in wireless sensor networks (WSNs). This article investigates a U-IRS-assisted data collection system in WSNs that employs the hover priority scheme. Given the energy constraints of UAV, the combined energy consumption from UAV moving/hovering and IRS reflecting elements configuration circuitry poses significant challenges to improving the system’s energy efficiency (EE). To address this challenge, we formulate a multiobjective optimization problem under the constraints of UAV and SN power budgets to make a tradeoff between EE and spectral efficiency. Due to the nonconvexity of the formulated problem, we divide the main problem into three subproblems: user association, the number of reflecting elements, and UAV trajectory optimization. An alternating optimization algorithm integrating the genetic algorithm, the CJ-BS-based cyclic iteration algorithm, Dinkelbach’s algorithm, and the successive convex approximation method is proposed to solve these subproblems. Simulation results demonstrate that the proposed solution outperforms the UAV hovering directly above each SN scheme.