In emergency communication scenarios, unmanned aerial vehicles (UAVs) can be used as an air relay to provide higher-quality communication for indoor users. When bandwidth resources are scarce, the use of free space optics (FSO) technology will greatly improve the resource utilization of the communication system. Therefore, we introduce FSO technology into the backhaul link of outdoor communication, and use free space optical/radio frequency (FSO/RF) technology to realize the access link of outdoor indoor communication. The deployment location of UAVs will affect not only the through wall loss of outdoor–indoor communication but also the quality of FSO communication, and, therefore, it needs to be optimized. In addition, by optimizing the power and bandwidth allocation of UAVs, we realize the efficient utilization of resources and improve the system throughput on the premise of considering information causality constraints and user fairness. The simulation results show that, by optimizing the location and power bandwidth allocation of UAVs, the system throughput is maximized, and the throughput between each user is fair.

This paper investigates the throughput optimization strategy in an unmanned aerial vehicle (UAV)-enabled emergency outdoor–indoor fairness communication scenario, with the UAV as a mobile relay station in the air, to provide outdoor–indoor communication services for users inside buildings. The occurrence of severe signal fading caused by outdoor transmission loss through wall loss as well as indoor transmission loss when the UAV forwards the information to the indoor users reduces the channel gain and degrades the system downlink throughput. To improve the downlink throughput of the system and ensure communication fairness for indoor users, we designed a joint UAV location deployment and resource allocation (JLRO) algorithm that optimized UAV three-dimensional (3D) deployment location, power and bandwidth resource allocation. The simulation results demonstrate the convergence and validity of the proposed JLRO algorithm, as well as its superiority compared to benchmark algorithms.

In the emergency scenario of Unmanned Aerial Vehicle (UAV) relay, link interruption caused by shortage of communication resources often occurs. Using spectrum sensing, UAV can expand communication bandwidth and ensure communication quality. However, spectrum sensing of UAV will increase energy consumption and reduce UAV dwell time. Aiming at the contradiction of energy consumption and communication quality, this paper proposes a relay sensing decision algorithm. Firstly, the spectrum sensing model and algorithm are established. Then, the outage probability is taken as the threshold value adjusting three-dimensional coordinates in the UAV relay sensing decision algorithm. Finally, we construct a UAV relay sensing decision algorithm, which adds the limit of unless outage probability threshold to the firefly algorithm to adjust the position of UAV. By adjusting the three-dimensional coordinates of UAV, the unless outage probability is guaranteed for UAV relay link. Through the simulation of building emergency fire scene, it is verified that the UAV relay sensing decision algorithm can automatically find the optimal UAV sensing position and ensure communication quality.