Energy-Efficient Wireless Powered Communications with NOMA in Multi-UAV Aided Networks

Abstract

This paper tackles the energy efficiency optimization in wireless communication networks, where multiple unmanned aerial vehicles (UAVs) deploy power transfer towards several energy receivers (ERs) to enable their uplink data transmissions through non-orthogonal multiple access (NOMA). Utilizing a formulated closed-form expression for energy efficiency (EE), a resource allocation mechanism aiming to maximize the system's EE is developed. To address this optimization problem, two algorithms are proposed that use Lagrangian optimization and gradient descent methods. For the simulations, three different cases, depending on the ERs' service demands, are considered. Numerical results along with comparisons are given and illustrated. The results show an enhancement in the energy efficiency for the cases that consider the needs of the ERs. Moreover, in all cases, the NOMA scheme's EE results are better than OMA with respect to the optimal charging time.