Impact of UAV Trajectory on NOMA-Assisted Cellular-Connected UAV Networks

The consideration of unmanned aerial vehicle (UAV) trajectory is of crucial importance in the performance evaluation of cellular-connected UAV networks. In this work, we consider a cellular-connected aerial user equipment (AUE) employed for surveillance and monitoring. The AUE moves along a given trajectory, while periodically transmitting to a terrestrial base station (BS) in the uplink, with a specific quality of service (QoS) requirement. To avoid the underutilization of spectrum resources, we enable simultaneous uplink transmissions of the AUE and a terrestrial user equipment (TUE) using power-domain uplink aerial-terrestrial non-orthogonal multiple access (NOMA). We take the trajectory of AUE into consideration and develop an analytical framework to compute the total rate coverage probability, i.e., the probability where both AUE and TUE are decoded, at a given transmission point in the trajectory. In addition, we numerically determine the minimum height of AUE to achieve a certain QoS constraint for different AUE target data rates and built-up areas. Our results show that, for a spiral trajectory, the minimum height increases as the AUE moves from cell center to the boundary, and as the severity of the environmental parameters increases.