# Energy-Efficient Clustering Scheme for Flying Ad-Hoc Networks Using an Optimized LEACH Protocol
## 2 Background  
### Flying Ad Hoc Networks (FANETs)  
After the mobile ad hoc mobile (MANET), vehicular ad-hoc vehicle (VANET), and with the help of wireless sensor networks, we have been able to move and operate new devices in a self-reliant way to create more complicated structures. In FANET, devices are commonly called unmanned aerial vehicles (UAVs), and UAVs have introduced a new network paradigm by which we can innovatively perform various operations. WSN comprises an autonomous sensor nodes network for environmental detection and monitoring of the region. These sensor nodes link together to form a wireless network arbitrarily placed in the required geographical region. All sensor nodes capture data and send it to the BS through wireless communication via other SNs. Each WSN node contains the four significant elements indicated in Figure 1. The power unit (usually batteries) is the only energy source to provide all other units, as follows:  
1. Wireless transmission unit, consisting of two modules of radio frequency for emission and reception that provide wireless connectivity for linking the node to the network. 2. Sensing unit, incorporating the data attained by one or more sensors, and an ADC (Analog to Digital Converter) for converting a sensor-produced analogue signal into a numerical signal. 3. Treatment unit, whereby the CPU, storage, and routing protocol are the main parts. This unit performs the protocols of communication that enable communication between nodes. As FANET's results in high mobility, stronger connectivity and expansion in device zones are the essential elements that differ from its predecessor MANET. Moreover, FANETs can travel independently in a three-dimensional space. It generalizes topologies from 2D to 3D by a free movement scheme due to the ability of the drones to run in 3D, as shown in Figure 2. Such a new technique has appealed to researchers and industry because it can provide the power to drive real-life applications. FANETs are commonly used to make connections with hard-to-access sites in regions with natural hazards and for military applications. The traditional networks can scan the damage with the help of FANETs and automatically shut down after a disastrous incident (such as a seism, cyclone, storm, flood disaster, and dam breakage). In addition, UAVs can be fitted to furnish a continuous  
Figure 1: WSN units. aerial view with cameras and other forms of sensors that are equipped to save lives for emergencies and help crews or firefighters. Direct contact from the UAVs to the BS on the ground can at some point be impossible in broad coverage areas. However, hop-to-hop communication can solve this problem, whereby a routing protocol identifies the best route/path from source to destination [5]. The highly mobile UAVs ensure that the topology of the network will change over time. Thus, it is one of the critical problems to identify and manage routes [6]. Due to the routing protocols, the discovery, establishment, and maintenance of routes between two nodes through communication are possible. These protocols can reduce overhead and bandwidth usage. A FANET routing protocol is considered more complicated than fixed network protocols because of features such as the dynamic topology algorithm, mutual intervention, limited battery capacity, and the UAV's limited resources. With the high mobility of UAVs in FANET, it is possible that a UAV may not be at a sufficient distance to communicate with one another. Hence, it is necessary to choose alternate routes by using routing information. This link can be established across intermediate nodes in several hops. In other words, communication cannot be contained on each device's range of action but the sum of the radius of action of each device. The mobility of a UAV is also very significant for deciding the contact pathways and their spatial structure. These routes are generally reorganized, and as a result, allow continuous movement and interconnection between the UAVs.