Abstract
When communication infrastructure is damaged due to natural disasters, employing unmanned aerial vehicle (UAV) as a flying base station (BS) and device-to-device (D2D) communication paradigms are among the essential strategies for seamless and reliable services. However, the communication reliability of the flying BS and the energy efficiency (EE) of the D2D communications may be degraded due to the shared spectrum coexistence of the UAV and D2D pairs. In this paper, we consider the uplink transmission to an UAV which is underlaid with D2D communication pairs randomly distributed on multiple frequency bands. For such a scenario, we derive tractable expressions for the successful transmission probability, the average sum-rate, and the EE of the network based on stochastic geometry principles, that perfectly match the simulation results. We also address the effects of D2D and UAV-connected users densities on the EE and sum-rate as performance metrics in the uplink scenario. Finally, some critical insights are provided based on the trade-off between different network parameters, and accordingly recommendations are given for maximizing the EE of such networks in post-disaster situations.