Dynamic UAV relay positioning for the ground-to-air uplink

In this paper we consider a collection of mobile single-antenna ground nodes communicating with a multi-antenna unmanned aerial vehicle (UAV) on a multiple-access ground-to-air wireless communications link. The UAV uses beamforming to mitigate the inter-user interference and achieve spatial division multiple access (SDMA). In addition, the UAV dynamically adjusts its heading in order to maximize a lower bound on either the ergodic sum rate of the uplink channel or the minimum ergodic rate of the worst-case user, using a Kalman filter to track the positions of the mobile ground nodes. We present simulation results that demonstrate the benefits of adapting the UAV heading in order to optimize the uplink communications performance.