A Cooperative Recharging-Transmission Strategy in Powered UAV-Aided Terahertz Downlink Networks

Abstract

Considering that unmanned aerial vehicles (UAVs) with the advantages of flexible deployment and high maneuverability have the limited energy to provide long-term seamless coverage, a cooperative recharging-transmission strategy is studied in this paper for the powered UAV-aided terahertz (THz) downlink networks, where a UAV-to-user THz sub-band association scheme is proposed for the THz frequency transmission to eliminate interference. Based on this, the minimum requirements of the wireless charging window and THz-transmitting window are derived. A minimization problem of minimum timeslot requirement is formulated to jointly optimize UAV placement and UAV-to-user THz sub-band association. The optimization problem is non-convex, and we propose an alternating optimization solution via iteratively solving placement subproblem and association subproblem. Specifically, we resort to the coalescent method of interior point and gradient descent algorithms to optimize UAV placement. The UAV-to-user THz sub-band association is solved as a knapsack problem by the transformation of association matrix. Simulation results validate the solution and demonstrate that the proposed strategy can achieve quasi-optimal performance compared with other contrasting strategies.