# Performance Evaluation of Multi-UAV Network Applied to Scanning Rocket Impact Area +
## 1 Introduction
This approach ensures a proper communication time to minimize the path length and discuss a method for locating and grouping sensors in an optimal coverage, also taking into account communication information between UAVs. [PERSON] and [PERSON] [33] review proposed mobility, positioning and propagation models for FANETs. This work highlights that the common limitation that affects such aspects is the lack of studies that assess the influence of UAVs on embedded communication devices. For this reason, it measures the impact of a UAV on the onboard Wi-Fi radiation pattern. In this work, the aircraft used to scan the area presents a flight range of up to 20 h. Two distinct man-machine-Interface (MMI) approaches are used: remote pilot interface and operator interface (just in case of emergency). As for the communication link for flight control and navigation messages, two different link radios are used: a 100-km range very-high frequency (VHF) uplink and S-band downlink to receive telemetry data and images from a single UAV as recommended in [20]. In order to perform U2U communication, ZigBee devices that work with an operating frequency of less than S-Band were chosen so that the signal suffers fewer attenuation effects and low manufacturing cost is obtained. The main contribution of this paper can be summarized as follows:  
* Based on the analysis of the various possible configurations of the communication network and the specific features to perform the area scan over the sea, an appropriate architecture is proposed for this particular application based on devices that support IEEE 802.15.4 standard and ZigBee communication protocol. This solution is capable of sending telemetry data and images between the UAVs using a FANET;
* A communication protocol is proposed for a FANET operating in the maritime area, being capable of transmitting telemetry images and data. Due to the particularities of the scenario and involved application, XBee Pro 900 HP S3B sensors were adopted. Besides, the system meets the following requirements:  
The UAVs send telemetry data on the scanned area and target locations periodically using control messages. If the image system embedded in a UAV locates a target, the communication system must send the image to the HUB node through the FANET, which sends it to the GCS. Due to the restrictions of the offshore area and the payload of XBee sensors, it is necessary to fragment the image, send the packets in fragments, perform the control of the image reception and, if necessary, request the retransmission of some lost packet. For this purpose, data and confirmation messages are employed. Thus, the GCS confirms to the UAV through a message that the image was received. * The communication protocol was validated by assessing different scenarios and controlled environments. The first scenario validates the wireless sensor network (WSN) throughput on a mesh network. The purpose is to check whether ZigBee sensors meet image system requirements to send messages according to the time required to sweep the area. The second scenario assesses the fault tolerance capacity of the ad hoc network to reorganize itself into a multi-UAV system. If an intermediate node fails, the network reconfigures itself by finding new routes in the FANET in all test conditions;* Simulation tests were performed to define a position for which the aircraft structure influences as little as possible the electromagnetic propagation of the antenna used by XBee sensors.