Merits of Collocating Uptilted Antennas on Terrestrial Base Stations for Aerial Coverage

Abstract

The integration of uncrewed aerial vehicles (UAVs) into future wireless networks introduces challenges in ensuring reliable aerial coverage, particularly for UAV-based user equipment (UAV-UE). Traditional terrestrial base stations (BSs) with downtilted antennas, referred to as dt-BSs, are designed primarily for ground users. They provide inefficient connectivity to UAV-UE due to weak sidelobe gains, and susceptibility to ground reflection (GR) interference as well as sidelobe interference from non-serving dt-BSs. To address this, we propose a hybrid cellular architecture that collocates uptilted antennas on a portion of existing dt-BS towers, referred to as ut-BSs. These support UAV-UE exclusively, minimizing impact on ground users. We consider realistic antenna radiation patterns and probabilistic line-of-sight (LoS)/non-LoS (NLoS) links between ut-BSs and UAV-UE. Using stochastic geometry, we analyze the UAV-UE coverage probability, accounting for interference from both dt-BSs and non-serving ut-BSs, along with GR-induced interference. Results show significant improvements in UAV-UE coverage with only a small density of ut-BSs. GR interference is notable at lower altitudes but diminishes beyond 500 meters. This study highlights the potential of our hybrid architecture to enhance the reliability and scalability of UAV communications in large-scale deployments. It also offers actionable insights for telecom operators considering the collocation of uptilted antennas within existing infrastructure to better support aerial connectivity.