# A Review of Flying Ad Hoc Networks: Key Characteristics, Applications, and Wireless Technologies
## 11 Conclusions  
This paper has presented a comprehensive review of FANETs, highlighting their characteristics, routing protocols, and new applications. UAV-based communication provides many benefits, and as such many solutions are being proposed and implemented by researchers exploring their possible employment. The main objective of this article has been to provide a thorough review of overall research in the area of FANETs, describing the different types of UAVs used in FANETs along with their main characteristics, applications, and routing protocols. This comprehensive review sought to find the most relevant publications addressing each of these topics. The main findings of this review are summarized as follows:  
* _UAV classification_: UAVs can be classified based on size, weight, altitude, range and endurance, application, flying mechanisms, air class, degree of autonomy, ownership, and type of engine. * _Main Characteristics of FANETs_: Node density, node mobility, changing network topology, communication range, radio propagation model, localization, power consumption, frequency band, cost-efficiency, versatility, agility, and network lifetime are the main characteristics of FANETs. * _Main Applications of FANETs_: The applications of FANETs can be classified into three main categories: _Multi-UAV cooperation_ (e.g., target detection/tracking, area monitoring, and surveillance), _UAV-to-ground tasks_ (e.g., relay networking, provision of on-demand base stations for mobile communication, intermittent networking), and _UAV-to-VANET collaborations_ (e.g., roadway traffic monitoring, data packet delivery, route guidance). * _FANET routing protocols_: FANET routing protocols can be classified into six main categories: _position-based, topology-based, delay-tolerant networks (DTNs), heterogeneous, cluster-based_, and _swarm-based_. * _UAV Mobility models_: The mobility models used by FANETs consist of pure randomized mobility models, time-dependent mobility models, path-based mobility models, group mobility model, and topology control mobility models. * _Integration of other technologies with UAV-networked systems_: UAVs have been integrated with various technologies, including augmented and virtual reality, IoT, cloud computing, fog and edge computing, cellular networks, and intelligent reflective surfaces. * _Main components of CBLUMS_: Cloud-based UAV managing systems includes three main layers: the UAV layer, cloud layer, control layer. * _Simulation Tools_: The available FANET performances analysis tools include _AVENS_, _CUSCUS_, _Simpleotic_, _UAVSim_, _UITSim_, _FANETSim_, _Netsim_, _OMNeT++_, _NS2_, _NS3_, _OPNET_, _ROS-NetSim_, _MATLAB_, _TOSSIM_, _QualNet_, _GloMoSim_, _YANS_, _ONE_, _SSFNet_, _FynetSim_, J-Sim_, _BomMotion_, _GAZEBO_, _AirSim_, _RoboNetSim_, _Mininet-Wifi_, and _SUMO_, each of which support different mobility models, operating systems, and programming languages. * _Future Directions_: When integrating new technologies with UAV-based communications, there remain several significant open challenges that need to be addressed, including the energy limitations of UAVs, the need for dynamic management of various resources (bandwidth, transmitting power, number of UAVs, UAV flight time), and the FANET security. An important contribution of this paper is our discussion of possible future UAV network application, which was made possible by a review of the main emerging technologies that are currently being integrated with FANETs. This discussion sheds light on the future of this research area and can open the path for new ideas further exploring the possibilities discussed in this article. Conceptualization, F.P., J.P.J.d.C. and E.P.d.F. ; methodology, F.P. ; formal analysis, F.P. ; investigation, F.P. ; writing--original draft preparation, F.P. ; writing--review and editing, E.P.d.F., J.P.J.d.C., R.K., N.I., W.H. and F.P. ; supervision, J.P.J.d.C. and E.P.d.F. All authors have read and agreed to the published version of the manuscript.