# Performance Evaluation of Multi-UAV Network Applied to Scanning Rocket Impact Area +
## 1 Introduction  
Unmanned aerial vehicles (UAVs) have been widely used in a large number of applications over the last years in many different fields, for example, environmental monitoring [1; 2; 3], visual coverage [4; 5; 6], natural disaster management [7; 8; 9; 10], among others. When scanning large areas, a multi-UAV system can execute a monitoring task more efficiently and faster than a single aircraft, with the possibility to acquire images simultaneously and from different points of view. A team of UAVs working according to an adequate collaboration strategy can overcome typical limitations in terms of autonomy and short-range associated with a single UAV, therefore covering larger areas and ensuring the fast execution of the mission, while also aggregating cost reduction, fault tolerance and scalability to the task [11]. Establishing a stable and reliable UAV network is a challenging task. Many issues should be addressed before its effective use in order to provide efficient communication among the UAVs. Differently from common ad hoc networks, flying ad hoc networks (FANETs) must deal with several hard constraints depending on the application, including high mobility and varying speeds of the UAVs, intermittency of communication links and dynamic changes in topology [12]. In order to preserve the quality of services and ensure the reliable transmission of packets between end nodes, routing protocols must address specific issues other than those found in conventional proactive or reactive schemes. The network must reorganize itself often and, sometimes, it may even get partitioned. Since autonomy is an important issue in UAVs, FANETs must deal with energy saving in order to increase the network lifespan [13]. Therefore, all components of the FANETs face distinct challenges to be solved. Some recent works have addressed improvements in the communication system through routing protocols [14; 15], Quality of Service (QoS) [16], distinct architectures [17; 18], resilience [19], as well as other characteristics that may bring additional reliability and safety to the system. Barreira do Inferno Launch Center (CLBI, _Centro de Lancamento da Barreira do Inferno_) is one of the Brazilian suborbital rocket launch centers, which is located in the city of Parnamirim, state of Rio Grande do Norte at the northeastern shore. During the launching chronology, before a rocket launching is performed, it is necessary to scan the predicted impact area in order to detect possible intruder boats and escort any ship found out of the restricted area. Nowadays, the impact area scanning procedure is executed by the CLBI using a manned aircraft (model EMB-110 Bandeirante), which involves a time consuming and expensive procedure. This task can be more efficient and cost-effective if performed by UAVs [20]. For basic training rocket and intermediate training rocket launchings, the rocket reach and radius of the impact area are within the range of a few kilometers, as it can be seen in Figure 1, where SBR-215 and SBR-217 correspond to restricted airspaces. The scanning procedure can be performed by a single UAV in this case [20; 21]. For larger rocket launching procedures, the reach and radius of the area to be scanned is also larger according to Figure 1, where SBR-213 is a restricted airspace. A single UAV will not be capable of performing the scanning procedure accurately, mainly due to time constraints. In such cases, a multi-UAV system composed of autonomous aerial vehicles is preferred instead due to their inherent ability to perform the scanning procedure in a fast and economically efficient way. When scanning the rocket impact area with a multi-UAV system, some aircraft may fly beyond the signal range of the base station (BS) antenna. In this case, some kind of communication infrastructure is required to transmit information between the distant aircraft and the BS.