  Unmanned Aerial Vehicle (UAV) technology is becoming more prevalent and more
diverse in its application. 5G and beyond networks must enable UAV
connectivity. This will require the network operator to consider this new type
of user in the planning and operation of the network. This work presents the
challenges an operator will encounter and should consider in the future as UAVs
become users of the network. We analyse the 3GPP specifications, the existing
research literature, and a publicly available UAV connectivity dataset, to
describe the challenges. We classify these challenges into network planning and
network optimisation categories. We discuss the challenge of planning network
coverage when considering coverage for flying users and the PCI collision and
confusion issues that can be aggravated by these users. In discussing network
optimisation challenges, we introduce Automatic Neighbouring Relation (ANR) and
handover challenges, specifically the number of neighbours in the Neighbour
Relation Table (NRT), and their potential deletion and block-listing, the
frequent number of handovers and the possibility that the UAV disconnects
because of handover issues. We discuss possible approaches to address the
presented challenges and use a real-world dataset to support our findings about
these challenges and their importance.
