Placement and Resource Allocation of Wireless-Powered Multiantenna UAV for Energy-Efficient Multiuser NOMA

TL;DR

This paper proposes an energy-efficient system where a wireless-powered multiantenna UAV optimally serves multiple NOMA user pairs by joint placement, power, and time allocation, significantly outperforming non-optimized alternatives.

Contribution

It introduces a joint optimization framework for UAV placement, WPT time, and power allocation in a wireless-powered NOMA system, employing novel decomposition and game-theoretic methods.

Findings

Optimized UAV placement improves energy efficiency.

Supermodular game guarantees convergence to Nash equilibrium.

Simulation results show substantial performance gains.

Abstract

This paper investigates a new downlink nonorthogonal multiple access (NOMA) system, where a multiantenna unmanned aerial vehicle (UAV) is powered by wireless power transfer (WPT) and serves as the base station for multiple pairs of ground users (GUs) running NOMA in each pair. An energy efficiency (EE) maximization problem is formulated to jointly optimize the WPT time and the placement for the UAV, and the allocation of the UAV's transmit power between different NOMA user pairs and within each pair. To efficiently solve this nonconvex problem, we decompose the problem into three subproblems using block coordinate descent. For the subproblem of intra-pair power allocation within each NOMA user pair, we construct a supermodular game with confirmed convergence to a Nash equilibrium. Given the intra-pair power allocation, successive convex approximation is applied to convexify and solve the subproblem of WPT time allocation and inter-pair power allocation between the user pairs. Finally, we solve the subproblem of UAV placement by using the Lagrange multiplier method. Simulations show that our approach can substantially outperform its alternatives that do not use NOMA and WPT techniques or that do not optimize the UAV location.