A new connectivity model for unmanned aerial vehicle communications and flying height optimization

This paper presents a new connectivity model for unmanned aerial vehicle (UAV) communications. We present closed-form formulas for the probability of line-of-sight as a function of UAV height and distance to a ground based receiver, based on a two-dimensional model of building and UAV locations. We show that our formulas exactly match Monte-Carlo simulated values, whereas the existing approach over-predicts by a factor of 2 to 3. We use the model to optimize the flying height for a UAV deployed as a mobile base station, where the goal is to maximize the number of possible connected users. We observe that the optimal height has a log-linear characteristic. We use this to present a closed-form formula for optimal height. We show that our techniques predict the height within 4% of realistic Monte-Carlo simulations, and significantly outperform existing approaches which are shown to over-predict by 40%-50%.