Joint Bandwidth and Position Optimization in UAV Networks Deployed for Disaster Scenarios

In this paper, we consider a disaster-affected area that has lost cellular connectivity. In such a scenario, we study a unmanned aerial vehicle (UAV) network deployed to restore the user connections to the core network. In particular, we propose a resource partitioning scheme for integrated access and backhaul in the downlink to sustain the user connections. First, we derive an analytical expression for the throughput coverage probability for the access (i.e., UAV to user) and the backhaul (i.e., terrestrial base station (BS) to UAV) links. Then, we investigate the optimal position of the UAV and the optimal partitioning of the frequency resources between the access and the backhaul links to maximize the coverage of the users. Our study highlights that as the number of users in the network and/or their throughput demand increases, the optimal UAV position moves towards the center of the disaster-affected area. Moreover, in that case, a higher fraction of the available frequency resources must be provisioned for the access links. On the contrary, when the backhaul throughput requirements are high, or when terrestrial BSs are sparsely deployed, the optimal UAV position is at the edge of the disaster-affected area. Thus, this study provides key system-design insights to a network operator to deploy ad hoc areal networks to extend cellular coverage.