Performance Analysis and Optimization of UAV-Assisted Networks: Single UAV With Multiple Antennas Versus Multiple UAVs With Single Antenna

In this article, we make a comparison between the following two unmanned aerial vehicles (UAVs) network models: 1) multiple UAVs equipped with a single antenna and 2) a single UAV equipped with multiple antennas (MAs). In order to assess the performance of the two network models, we derive closed-form expressions for the outage probability, average symbol error probability, ergodic capacity, and energy efficiency of both models. After that, we formulate a joint optimization problem to obtain the optimal power values and UAV altitudes using the particle swarm optimization technique. We consider in the first scenario both uniformly and nonuniformly distributed UAVs assuming Nakagami- <tex-math notation="LaTeX">m</tex-math> fading channels. Numerical results are obtained for different simulation scenarios to validate our proposed model, followed by conclusions to show its effectiveness. The results show the superiority of the multiple uncorrelated antennas single UAV model over a single antenna multiple UAV model. Moreover, several comparisons have been performed between blanket transmission mode (BTM) and single transmission selection mode (STSM) for the multiple UAVs model, which reveal that the BTM outperforms the STSM for different systems parameters.