Generalized UAV Selection With Distributed Transmission Policies

Unmanned aerial vehicle (UAV)-aided communications is a promising emerging technology that will be adopted in the next generation communication networks. In this paper, a number of advanced cooperative UAV-aided communication solutions is proposed and evaluated, which considerably improve the performance of traditional terrestrial networks. Specifically, two generalized multi-UAV-selection schemes are introduced, depending on whether a direct link between the source and the destination is available or not. Once the UAVs have been selected, they may retransmit the source message to the destination using distributed space-time coding, or, in the presence of channel state information, distributed beamforming. A number of metrics to evaluate the performance on a realistic channel model was adopted, including the end-to-end outage probability (OP), the so-called goodput, and the average number of path estimations, as well as the total UAV communications power consumption. Exact expressions for the OP were obtained in terms of finite sums. Moreover, convenient closed-form expressions for the asymptotic OP were derived, valid for large numbers of UAVs, which are also very accurate for few UAVs. All results were compared with numerical simulations, which clearly depict the performance improvement induced by the proposed schemes as well as the impact of various system and channel parameters to the performance.