## 5 Conclusions  
The potential of FANETs can increase in the coming years with the advent of new communication technologies and standards such as 6G, the Internet of Things (IoT), and connected autonomous vehicles (CAVs). The benefits that FANETs can offer are immeasurable (coverage extension, application in emergency communications, search and rescue, agriculture, etc.). When deploying FANETs, it is essential to be able to find the path that a packet must follow to reach its destination. Due to the characteristic constant changes in the network topology of FANETs, the selection of the routing protocol is a crucial task for effective deployment and successful operation. After detailing the different routing protocols that have been proposed for FANETs, this paper performed a case study comparing the performance offered, in terms of throughput and packet loss, of three proactive routing protocols: OLSR, BATMAN-ADV, and Babel. The scenario studied could simulate a coverage extension scenario in emergencies, search and rescue, or remote surveillance. The results obtained showed that Babel achieved higher performance in the studied metrics, outperforming OLSR and BATMAN-ADV. Besides, it was shown that BATMAN-ADV performed significantly worse than OLSR and Babel due to its low frequency of routing-table updating. In particular, the sending period of messages in charge of finding alternative routes in BATMAN-ADV is 1 s (OGM interval). In FANETs, the network topology can vary a lot in 1 s, hence discouraging its use for FANETs. As future work, we consider that an extension of the routing protocols to be evaluated would be a logical next step, employing a more significant number of UAVs with different characteristics and comparing experimental results and propagation models such as those presented in [77]. Conceptualization, M.-D.C.; methodology, M.-D.C. and J.-C.S.-A. ; software and tests measurements, A.G.-P., A.-M.M., and J.-C.S.-A. ; formal analysis, A.-M.M. and M.-D.C.; writing, A.G.-P. and M.-D.C. All authors have read and agreed to the published version of the manuscript. Figure 4: Average packet loss (%) vs. distance (meters) for each protocol and frequency band. **Funding:** This research was funded by the AEI/FEDER, UE project grant TEC2016-76465-C2-1-R (AIM), project SPID202000X116746 SV0 (AriSe2: FINe), and 20740/FPI/18. Fundacion Seneca. Region de Murcia (Spain). **Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results. **Abbreviations**  
AeroRP Aeronautical Routing Protocol. AODV Ad Hoc On-Demand Distance Vector. AODVSEC AODV Security. APAR Ant Colony Optimization-Based Polymorphism Aware Routing Algorithm. ARPAM Ad Hoc Routing Protocol for Aeronautical Mobile Ad Hoc Networks. BATMAN Bent Better Approach to Mobile Ad Hoc Network. BATMAN-ADV BATMAN-Advanced. CAUN Clustering Algorithm of UAV Networking. CBLADSR Cluster-Based Location-Aided DSR. CE-OLSR Cartography-Enhanced OLSR. COLRS  
Contention-Based OLSR. CRUV Connectivity-Based Traffic-Density Aware Routing Using UAVs for VANETs. DCR Data-Centric Routing. DOLRS  
Directional OLRS. DSDV Destination-Sequenced Distance Vector. DSR Dynamic Source Routing. DTM Disruption-Tolerant Mechanism. DTN Delay-Tolerant Network. FANET Flying Ad Hoc Network. FSR Fisheye-State Routing. GCS-R Ground Control System-Routing  
GDSTR-3D Greedy Distributed Spanning Tree Routing 3D. GGF Greedy Geographic Forwarding. GHG Greedy-Hull-Greedy. GLRS Geographic Load-Share Routing. GPMOR Geographic Position Mobility-Oriented Routing. GPSR Geographic Greedy Perimeter Stateless Routing. GRAA Geographic Routing Protocol for Aircraft Ad Hoc Network. GRG Greedy-Random-Greedy. HRP Hybrid-Routing Protocol. HWMP Hybrid Wireless Mesh Protocol. LANMAR Landmark-Routing Protocol. LAROD Location-Aware Routing for Opportunistic Delay Tolerant. LCAD Load Carry and Deliver Routing. MANET Mobile Ad Hoc Network.