# Cluster-Based Control Plane Messages Management in Software-Defined Flying Ad-Hoc Network  
[PERSON]  
1  
[PERSON]  
1  
[PERSON]  
1  
[PERSON]  
1  
[PERSON]  
1  
2  
2  
2  
3  
4  
5  
6  
7  
8  
9
10  
11  
[PERSON]  
1  
1  
2  
3  
4  
5  
Footnote 1: email: cc.c. humans' eyes in the sky, and UAVs must be flying and monitoring events in a coordinated fashion for a long period with reliability [10]. In FANET scenarios, UAVs must collaborate, and their behaviors (both the data transmission and the UAV movement) must be effectively controlled to maximize the FANET benefits and application performance [11]. In this way, a decentralized approach [6] to manage FANET include more complexity to synchronize information with all network nodes, requiring more control messages to be transmitted across the FANET, and can increase total power consumption. On the other hand, a centralized UAV controlling system can make optimized decisions based on the global UAV context information [12]. A centralized controller node must deal with the mobility trajectory of UAVs to avoid UAV collisions or improve application performance. It also needs to determine data routing paths, change packet transmission parameters (data rate or transmission power) due to performance or energy reasons. Hence, FANET could be managed by a Software Defined Network (SDN) [13] composed by a group of UAVs with a central controller entity [14]. In turn, SDN-FANET [12] implements the concept of SDN into FANET to separate the control and data plane, and to provide network programmability [15]. The FANET control plane programmability means to perform UAV placement and replacement, to improve the application performance, to determine optimal data routing paths, and other control tasks. The SDN-FANET controller considers the global UAV context information, such as UAV positions, movement trajectories, and residual energy, to perform all control functions. SDN-FANET provides flexibility to network management, where the network plane can be programmed to meet particular application requirements [16]. SDN-FANET controller requires accurate global UAV context information to prevent UAV collisions, optimize the UAVs' movements, establish a routing path, and other decision making tasks [11]. In this way, the controller node must receive UAV context information with low packet loss to be aware of the UAV status for decision making, which is achieved by reliable control message dissemination [12]. However, control message dissemination with low overhead, and high performance is not a trivial task, due to particular characteristics of FANET, i.e., high mobility, failures in UAV to UAV communication, and short communication range [17]. The network topology changes quickly even if UAVs movements are controlled, leading to frequent control message dissemination, which increases the network overhead and interference, disconnection problems, increased latency, and packet losses [18]. In addition, FANETs are deployed for highly sensitive applications that require reliable transmission, but the SDN-FANET could share the same wireless medium for data and control messages. Under these circumstances, to keep FANET's applications and services more reliable, stable, and active, it is essential to design an efficient and reliable control message transmission for FANET operations [19]. It is essential to predict UAV information without control message transmission, reducing bandwidth consumption, and signaling overhead. For instance, based on mobility or energy consumption prediction algorithms, the controller can change the frequency control message dissemination. Also, for large-scale environments, it might be required multi-hop communication to disseminate control messages, which can be achieved by deploying multiple local controllers that are responsible only for forwarding control messages to/from the central controller [11].