The Impact of Deployment Height on the Mean Delay in Large UAV Networks

Unmanned Aerial Vehicles (UAVs) are widely recognized as important network elements in future Non-Terrestrial Networks (NTNs) being proposed for 6G. As client devices, UAVs are expected to have reliable and low-latency network connectivity to perform mission-critical tasks. In this paper, we analyze the mean connection delay between a large cohort of UAVs deployed at a given height and their supporting terrestrial infrastructure, when network capacity is limited by co-channel interference. By modeling the UAVs and the terrestrial Base Stations (BSs) as spatial processes, we establish necessary and sufficient conditions for the finiteness of the mean delay in both Air-to-Ground (A2G) and Ground-to-Air (G2A) scenarios. Our analysis reveals a phase transition behavior with respect to the corresponding closed-form order parameter. Interestingly, these parameters are independent of network height; a close examination of these order parameters establishes the intricate relationship between packet size, channel access probability, and the spatial intensities of the UAV and terrestrial BS processes required for the finiteness of the mean delay. Our analysis also permits an analysis of the mean delay in terms of these order parameters via series expansion with correction terms for non-zero height.