I. Introduction
Unmanned aerial vehicles, also known as drones, have been attracting significant attention from industry, academia, and the military by being cost-effective, available, versatile, and having high maneuverability. Various applications such as entertainment, package delivery, border surveillance, and remote sensing are a few examples to name [1]. Regardless of the intended application of the aerial vehicle, reliable C2 communication is crucial in all application domains to ensure safe operation. Additionally, high data rate communication is of significant importance in UAVs' applications in disaster relief, augmented reality, and environmental and infrastructure monitoring [2]. BVLOS operation, in turn, paves the way for various new applications of autonomous UAVs. However, it needs an ultra-reliable low latency communication [3]. Technologies such as WiFi [4], LoRA [5], and WiMAX [6] are available for UAV communication. However, the short communication range of WiFi, the low bandwidth of LoRA, and the latency, as well as the lack of support for highly mobile users in WiMAX, are the limiting factors that make the utilization of aforementioned technologies more concerning. More importantly, these technologies do not often meet the security expectations for UAV communication. The wide deployment, availability, high data transmission rates, reliability, and security of cellular networks make them ideal candidates for UAV communication. However, cellular networks are essentially designed and optimized to serve terrestrial users and might not be ready to serve aerial users, without modifications. Besides 3D coverage gaps due to cellular antennas being tilted toward the terrestrial users, frequent handovers, interference caused by UAVs to neighbor towers, mobility among different providers to maintain connectivity, and UAV identification are among the challenges of serving drones by cellular networks.