# Dynamic Routing in Flying Ad-Hoc Networks Using Topology-Based Routing Protocols
## 1 Introduction  
During the past few years, the exponential progress in the making of small unmanned aerial vehicles (UAVs) has helped create the foundation of a new kind of network, referred to as flying ad-hoc networks (FANETs). Due to their versatility, adaptability, and easy deployment, FANETs are becoming a promising solution for various military and civilian applications, such as disaster inspection [1], search and rescue operations [2], border surveillance [3], forest fire detection [4], relaying networks [5; 6], wind estimation [7], civil security [8], agricultural purposes [9], and traffic monitoring [10]. FANETs are essentially an ad-hoc network created by multiple small UAVS, which allows portable and flexible communication solutions in areas without infrastructure. The UAVs are hereby equipped with sensors, an on-board monitor, and a GPS module that may operate autonomously or via remote control. In order to avoid the limitations imposed by the conventional infrastructure-based communication architecture in a disastrous situation, FANETs are quickly deployable, self-configured, and offer a cost-effective communication data network [11]. While FANETs have the ability to collect and share the gathered information among the UAVs, they can also deliver it to the ground station. In addition, if some of the UAVs are disconnected during the mission due to weather conditions, they still havethe ability to stay connected to the network through the other UAVs. With the help of multi-hop ad-hoc networking schema, it can remove obstacles such as network failure, limited guidance and short-range communication, which normally arise in a single UAV system [12]. On the one hand, such unique characteristics make FANETs a suitable solution for diverse application scenarios; but on the other hand, it also creates some challenging communication and networking issues between the multiple UAVs [13]. The basic problem with FANETs is the cooperative communication among the UAVs. Therefore, routing becomes an important and compulsory task to better assist the transmission of packets between the UAVs. The FANETs applications are mostly supported by multi-hop communications, where the average speed of a UAV can span from almost 30-460 km/h in a three-dimensional environment [14]. In essence, the topology of the network changes quickly, which results in a link variation problem [15]. Additionally, frequent topology changes also enhance the latency, packet loss, and signaling overhead. Furthermore, FANETs are deployed for highly sensitive applications that demand guaranteed data transmission in a reliable, robust and cost-effective manner. Under these circumstances, designing and choosing appropriate routing protocols are essential in order to keep FANET applications and services more stable and active. To formulate solutions for routing issues in FANETs, the existing mobile ad-hoc network (MANETs) and vehicular ad-hoc network (VANETs) routing protocols are tested. These are mainly characterized into topology-based, swarm-based, and position-based protocols. Topology-based routing protocols exploit IP addresses to use the existing link information to forward data packets on the optimal path. These protocols require topological information from the communicating UAVs in order to establish and maintain the optimal path. Swarm-based routing is inspired by the natural behavior of social insect communities, such as being self-organized, self-adaptive and cooperative, in order to find the optimal path. However, the main failing of swarm-based routing is high latency due the high mobility of UAVs. In position-based routing protocols, packet forwarding is done on the basis of the geographic position of the UAVs. The main disadvantage of position-based routing is the transmission of stale information about the route during the frequently changing positions of the UAVs. Therefore, we explicitly focus on topology-based routing protocols in this article.