The main goal of this letter is to obtain models for path loss exponents and shadowing for the radio channel between airborne unmanned aerial vehicles (UAVs) and cellular networks. In this pursuit, field measurements were conducted in live LTE networks at the 800 MHz frequency band, using a commercial UAV. Our results show that path loss exponent decreases as the UAV moves up, approximating freespace propagation for horizontal ranges up to tens of kilometers at UAV heights around 100 m. Our findings support the need of height-dependent parameters for describing the propagation channel for UAVs at different heights.
Aerial users, such as unmanned aerial vehicles (UAVs), experience different radio propagation conditions than users on the ground. This is a concern regarding the integration of such users into cellular networks in the near future. This letter investigates the impact of uplink transmissions from an aerial user equipment. Full buffer transmissions were performed by a device at ground level and also flying attached to a UAV at 100 m height. The field measurements show a higher number of cells affected by the aerial transmission, with an increase of up to 7.7 dB in the interference over thermal noise in cells within 15 km of the test location. This letter also assesses two strategies to reduce the uplink interference caused by aerial users: 1) UAV's cruise height control and 2) directional transmissions. Results show the directional transmission is a more promising technique, and has the advantage of not reducing the uplink received power. Index Terms-UAVs, air to ground channel, aerial communication.
I. INTRODUCTIONU NMANNED Aerial Vehicle (UAVs), also known as drones, are experiencing a market surge boosted by technological developments in recent years. Data connectivity is one of the key enablers for beyond visual line-of-sight (BVLOS) flight ranges, which can help to unleash an emerging potential. Besides the control link between UAVs and their users, many applications may require high data rate connectivity, such as surveillance, infrastructure monitoring, and Manuscript
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