Wireless Channel Characteristics for UAV-Based Radio Access Networks in Urban Environments

The use of unmanned air vehicles (UAVs) as "flying base stations" is gaining significant traction in the scientific and industrial community. Such UAV-based wireless networks could be quickly deployed to increase the range of a network or to replace a damaged infrastructure in emergencies. One crucial requirement of UAV-based communication networks is understanding the distinctive features of UAV propagation channels, especially the angular spreads and delay spreads that dictate the performances of Orthogonal Frequency Division Multiplexing (OFDM) technology and Multiple-Input Multiple-Output (MIMO) system. In this paper, we analyze the angular spreads and delay spreads of the air-to-ground wireless channels based on extensive ray-tracing simulations. Our results indicate that, contrary to expectations, the angular spreads and the delay spreads at the ground-based Mobile Terminals (MTs) are more substantial in Line-of- Sight (LoS) conditions than in Non-Line-of-Sight (NLoS) conditions, which can be explained by the particular geometry of the air-to-ground channels. These results also make meaningful suggestions for the UAV-based communication system design.

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