## 1 Introduction  
Unmanned aerial vehicles (UAVs, also known as drones) have become more and more popular due to the swift uptake of technological advancements such as inexpensive Wi-Fi radio connections, navigation systems, sensing, lightbridge technology, multi-SIM LTE/4G, 5G, and integrated devices. UAVs are currently widely used in military operations, civilian applications, and academic research. UAVs can easily connect to a network and may operate with varying levels of automation, whether remotely controlled by a ground station administrator or entirely autonomously by an embedded system [1; 2]. UAVs can significantly improve wireless communication networks. UAV networks can be categorized into two types: single-UAV networks and multi-UAV networks. A single-UAV network is typically a large UAV connected directly to a ground control station and a satellite network. This type of network is frequently employed to carry out specific missions. A single UAV network is installed using complicated hardware communication technologies to maintain connectivity with the ground control station. It is noteworthy that if the UAV fails, the operation will be terminated. On the other hand, in a multi-UAV network, multiple UAVs are connected to one another, as well as to a base station, sensors, and a satellite. A multi-UAV network surpasses a single UAV system in terms of survivability, dependability, mission completion time, and redundancy. This implies that even if one of the UAVs fails during an operation, the operation may be completed by other UAVs [1]. A flying ad-hoc network (FANET) [3] is a type of multi-UAV network using an ad hoc communication method. In particular, a FANET (or UAV ad hoc network) is an autonomous, self-organizing network in which UAVs not only link to neighboring UAVs to transmit data packets from the source to the destination but also use their neighbor's UAVs to relay data. UAV ad hoc networks are made up of all flying UAVs, but only some of them can communicate with satellites or base stations. Consequently, all UAVs may communicate with each other in addition to the base station. A UAV ad hoc network provides several benefits, including flexibility, greater accuracy, more economics, continuity, and increased speed [4]. Data transfer between UAV nodes requires the use of a routing protocol. The requirements of FANETs [5] are not fully addressed by the conventional ad hoc network routing techniques for mobile ad hoc networks (MANETs) and vehicular ad hoc networks (VANETs). A UAV ad hoc network has additional specific features such as rapid mobility, three-dimensional space flight, quick topology changes, frequent breaking connections, network segmentation, low node density, and limited energy that make effective routing protocols complex [6; 7]. Furthermore, the quality-of-service (QoS) requirements for diverse UAV applications vary greatly. For example, certain applications, such as data collection and mapping, may tolerate delays, while other applications, such as search and rescue missions, demand a real-time data stream with as few delays as possible. As a result, a lot of research has been conducted to implement routing protocols that take into consideration the application needs as well as the unique aspects of UAV ad hoc networks. To highlight the suggested modifications in well-known ad hoc routing protocols, several earlier studies compared ad hoc routing protocols based on their specific UAV use cases [8]. In this paper, we evaluate the efficacy of four routing protocols in a SAR scenario in which a rectangular search area is well-defined and the mission is completed more quickly by using several UAVs. Additionally, we take into account a randomized search scheme that is motivated by a time-dependent mobility model. Nevertheless, the research does not take into account planned search schemes or circle search schemes. The main contributions of this paper are the following:  
1. This research study evaluates the efficiency of four well-known routing algorithms in a UAV ad hoc network.