Impact of Multipath on Anchors Selection Strategies for UAVs Positioning in Mobile Networks

Positioning is gaining increasing interest in mobile systems, due to its potential integration with many 5G verticals. Also in the context of non-terrestrial networks, positioning of aerial vehicles constitutes a crucial element of the communication, control, and applications of these systems. In particular, Unmanned Aerial Vehicles (UAVs) have become strategic actors in this technical and economic trend. One of the peculiarity of UAV positioning in mobile networks is that the signal of many BSs, or anchors, could be received and employed for the estimation since the propagation channel conditions tend to improve as the altitude increases, including the fundamental LoS availability. On the other hand, this positive aspect poses serious issues in terms of computational complexity, channel occupation and latency if an appropriate selection of the available anchors is not performed. In this work we investigate and discuss the performance of several strategies for the selection of available anchors in realistic propagation scenarios, with an emphasis on the impact of multipath, according to the 3GPP channel models for aerial vehicles. The application of these strategies to channels affected by multipath with the use of a standard least squares positioning technique reveals interesting properties and design directions for a feasible solution of the anchors selection problem.