# TARCS: A Topology Change Aware-Based Routing Protocol Choosing Scheme of FANETs
## 1 Introduction  
Mobility is one of the most prominent features of mobile ad hoc networks (MANETs) and one of the important factors affecting network performance. Being a typical subset of MANETs, the node mobility in flying ad hoc networks (FANETs) [1; 2; 3] is stronger and severely impacts the network performance (Figure 1). FANET has some unique characteristics compared to MANET and VANET (Table 1). In FANETs, high-speed moving nodes usually need to complete multiple tasks, such as search/exploration,  
Figure 1: MANET, VANET and FANET. reconnaissance/patrol, or target tracking. Different task scenarios could have corresponding node mobility models [1]. When the task changes, the node mobility mode (such as node motion speed, direction, distance, etc.) changes accordingly, which will cause the network topology to change rapidly and seriously affect the network performance. The main research object of this paper is highly dynamic FANETs. Specifically, it corresponds to the FANETs listed in Table 1 in which the nodes move fast and the network topology changes drastically. The characteristics of the FANETs discussed in this paper are: small and medium-sized networks, high mobility nodes far from the ground at high altitudes, sufficient node energy and frequent network topology changes. In practical applications, FANETs encounter different application scenarios when nodes complete complex tasks. Nodes move in different ways in different scenarios, which causes large changes in the network topology. Traditionally, nodes cannot perceive this change, nor can they adapt quickly to it, so the network performance will deteriorate dramatically. The main purpose of this paper is to find a method by which nodes in a network can perceive changes of topology and adjust the routing strategy appropriately when the topology changes greatly, so that the network performance could be maintained at a high level. The most concerned network performance is the packet delivery ratio, followed by the average end-to-end delay, the average jitter, and finally the network throughput. Many routing protocols have been proposed for mobile ad hoc networks [4]. Each protocol has its own characteristics and application scenarios. For example, the Optimized Link State Routing Protocol (OLSR) [5] is suitable for high-density MANETs, and the Destination-Sequenced Distance-Vector Routing (DSDV) [6] is more suitable for small-scale MANETs. When the scenario is complex and the network topology changes rapidly, a single routing protocol cannot meet the requirements of the variable node mobility mode, nor can network performance be guaranteed. Accurate perception of the surrounding environment and appropriate adjustment strategies of nodes have become the trends of adaptive routing protocols with the increasing requirements of quality of service (QoS). In response to the above objectives, this paper proposes a solution for choosing routing protocols in highly dynamic FANETs, namely TARCS (topology change aware-based routing protocol choosing scheme). The TARCS scheme is divided into the following steps:  
Firstly, a topology change sensing method is proposed, which can measure the topology change between nodes of a high dynamic FANET, and a mobility metric TCD, the topology change degree with several levels is defined to quantify the perceived results.