Unmanned aerial vehicles (UAVs) as aerial base stations have attracted great attention in emergency communication networks due to flexible deployment. With the popularization of smart devices, the demand for multimedia services is increasing in disaster relief. Therefore, it is very important to significantly improve throughput of unmanned aerial vehicle base station (UAV-BS) while ensuring qualityof-service (QoS) of multimedia traffic. In this paper, we consider a UAV-BS to serve a group of users in the downlink who have different statistical delay-bound QoS requirements in an emergency situation. We formulate a problem to maximize the sum statistical-QoS-guaranteed throughput (effective capacity) of all users by jointly optimizing the UAV's 3D location, power and bandwidth allocation under each user's statistical QoS requirement constraint. The formulated problem is a non-linear non-convex optimization problem, which is very difficult to solve. To this end, we propose an efficient iteration algorithm based on the block coordinate descent and successive convex optimization techniques to solve it. Specifically, we decouple the primary problem into three sub-problems, which can be approximated as easy-to-solve convex optimization problems. In each iteration, three sub-problems are alternately optimized. Finally, numerical simulation results prove the effectiveness of our proposed algorithm compared with benchmarks.
INDEX TERMS UAV, unmanned aerial vehicle base station (UAV-BS), statistical QoS, successive convex optimization I. INTRODUCTION
A. BACKGROUND AND MOTIVATIONC OMMUNICATION plays an indispensable role when the natural or man-made disasters occur. As the traditional communication network is based on the infrastructure, it will be damaged and cannot be rebuilt to restore communication in a short time [1], [2]. Besides, the smart phones of most ordinary users do not have the ability to directly connect to satellites. Recently, UAV is considered to be a promising technology to quickly provide wireless services because of its cost-effective, swiftly deployed , high mobility. [3], [4]. For this reason, more and more researches have begun to focus on integrating UAVs into emergency communication networks as aerial base stations [5], [6] or relays [7], [8]. However, some disasters occur in a large area and the communication facilities are severely damaged, such as earthquake and tsunami, the UAV cannot find a backhaul node on the ground to connect to the core network. Due to the low-earth orbit (LEO) satellite system operating in the space, so it hardly affected by the disaster. LEO satellite networks also have short transmission delay, large bandwidth and small path loss characteristics, etc [9]-[11]. Attracted by above reasons, LEO satellites are very suitable as backhaul nodes when lacking ground facilities [12].With the assistance of multimedia services, the rescue efficiency can be greatly improved. For example, the command center can obtain real-time video of the rescue scene, so as to issue accurate rescue...