The use of Unmanned Aerial Vehicles (UAVs) to provide cellular communication in rural areas, disaster-hit regions, or during temporary events is gaining increasing attention due to its flexible deployment and energy efficiency compared to fixed terrestrial infrastructures. However, UAVs experience significant challenges such as the limited wireless connectivity provided by Ka-band frequency, and their flying time is constrained by the energy consumed during the data transmission and the complexity of the Baseband Unit (BBU) implementation. Using different lower layer functional split options (e.g., 7-1, 7-2, 7-2x, and 7-3), this paper provides a theoretical and simulation analysis of the 5G New Radio (NR) physical layer specifications to achieve a fronthaul bandwidth that can be supported by the Ka-band. These functional split options are then compared in terms of fronthaul bandwidth, theoretical throughput, connection density, number of functions deployed at the UAV, and the energy consumption of the fronthaul transmission to determine which functional split option is better suited for a multi-layered Non-Terrestrial Network (NTN)
