System Cost-Oriented UAV Deployment for Integrated Access and Backhaul Networks

Unmanned aerial vehicles (UAVs) have emerged as a promising solution to provide wireless data access for ground users (GUs) in various applications. In the scenario where GUs are far away from the gateway, both the access and backhaul links in UAV networks significantly affect the system performance. In this paper, we study the UAV deployment problem in an integrated access and backhaul network (IABN), where a number of UAVs are deployed as aerial base stations (ABSs) and aerial relays (ARs) to forward GUs $^\prime$ data packets to the remote gateway via multi-hop transmissions. Aiming at minimizing the system cost, which is defined as the weighted sum of UAV deployment cost and the energy consumption required for data transmission, a constrained system cost minimization problem is formulated, where the joint UAV deployment, GU association, route selection and resource allocation strategy is optimized. To solve the formulated non-convex problem, we propose an alternative iteration method, which includes two subalgorithms. For the first subalgorithm, we focus on the optimal design of the access links and propose a joint ABS deployment and resource allocation algorithm. Specifically, a modified K-means based clustering scheme is proposed to determine ABS deployment and GU association strategy, then an iterative Lagrange-based power allocation strategy and a greedy Kuhn-Munkras algorithm-based subchannel assignment strategy are presented, respectively. Given the obtained ABS deployment strategy, for the second subalgorithm, we then design a joint AR deployment, route selection and power allocation scheme for the backhaul links and propose a minimum circle algorithm-based AR deployment and route selection strategy. Finally, the suboptimal solution is obtained by alternatively handling the two subalgorithms. Numerical results show that the proposed UAV deployment algorithm can achieve a 19% performance gain over the existing scheme when the packet size is $6\times 10^{6}$ bits and system bandwidth is $0.5\times 10^{6}$ Hz.