CONIX Publication

Unmanned aerial vehicles provide new opportunities for various performance improvements in future wireless communications systems. For example, they can act as relays that extend the range of communication link and improve the capacity. Unlike conventional relays that are deployed at fixed locations, UAVs can change their positions to optimize the capacity or range on demand. In this paper, we consider using a swarm of UAVs as amplify-and-forward MIMO relays to provide connectivity between an obstructed multi-antenna equipped source and destination. We start by optimizing UAV placement for the single antenna case, and analyze its dependence on the noise introduced by the relay, its power gain and transmit power constraint. We extend our analysis for an arbitrary UAV swarm, and show how MIMO link capacity depends on swarm distance from source and destination as well as positions of UAVs within the swarm. We show that capacity is maximized for UAV positions that orthogonalize MIMO channels from source to UAV swarm, and from UAV swarm to destination. As a result, we demonstrate that the optimized swarm placement can boost capacity up to three times compared to random placements.