LAUSR

Unmanned aerial vehicle (UAV)-assisted heterogeneous network has drawn great research interests as it can significantly improve the capacity and coverage of cellular networks. An UAV can act as a flying base station (BS) or a relay when the regular terrestrial infrastructure is malfunctioned or overloaded. However, the deployment of UAV-mounted communication infrastructure is confined by the limited on-board energy and short battery life. To prolong the lifetime of each UAV, connecting it with a ground charging station (GCS) through a tether could be a promising and feasible solution. In this paper, we aim to maximize the sum rate of all users by jointly optimizing the user association, resource allocation and placement of the GCSs and the aerial UAVs. In addition, the constraint of each user's quality of service (QoS) requirement and total available resource are considered. To tackle this problem, we propose a cyclic iterative algorithm to efficiently obtain suboptimal solutions. Specifically, the primal problem is decomposed into three subproblems, i.e., the TUAV placement problem, the resource allocation problem and the user association problem. Then, the three sub-problems are alternately and iteratively optimized by using the outputs of the first two as the input for the third. Numerical experiments demonstrate that our proposed algorithm outperforms baseline algorithms under different setups.