Lifetime Maximization for Uplink Transmission in UAV-Enabled Wireless Networks

The use of unmanned aerial vehicles (UAVs) as aerial wireless base stations has been recognized as an effective approach to on-demand deployment for providing services during a temporary event or emergency situation. High UAV mobility can be fully utilized to create line-of-sight connection and alleviate
cross-link interference. While most of the prior works have studied UAV deployment, trajectory design and resource allocation strategies for improving the network throughput or energy efficiency, in this paper, we are interested in prolonging the lifetime of ground users for communications. The lifetime is defined as the communication time for the ground user before its battery is
exhausted. We consider a frequency division multiplexing (FDM) uplink system where the ground users are served by multiple UAVs. We formulate a joint user association, power control, bandwidth allocation and UAV deployment problem for lifetime maximization, and propose an efficient approximation algorithm
through judicious problem reformulation and successive convex approximation (SCA) techniques. For the scenario with only a single UAV, we show that the problem can be globally solved by simple bisection. Simulation results are presented to demonstrate that the proposed algorithms can achieve near-optimal performance and greatly outperform the heuristic methods.