# Communication Interface Manager for Improving Performance of Heterogeneous UAV Networks
## 1 Introduction  
The application of unmanned aerial vehicles (UAV) is proving to be extremely useful in a variety of areas, from agriculture to military missions [1, 2]. The need to exchange messages appears in many of these applications, either in the form of UAV-to-UAV (U2U) or UAV-to-base (U2B) communications. This allows remote access to difficult areas, where video transmission and additional measurement data traffic are needed, such as in applications for border and cave monitoring, natural disaster monitoring, search and rescue (SAR) missions, and others [3]. Flying ad hoc networks (FANET) is a denomination used to represent an ad hoc network among UAVs. It promotes network scalability, given the capacity to add and remove UAVs from the network. It also aims to ensure network survivability since communication does not rely in a single node (UAV). However, several challenges still prevent the complete establishment of FANETs [4, 5], for example, the demand for reliable wireless communications to allow sending and receiving messages with lower risk of loss. The main issues are maintaining reliable connections between high-mobility nodes, signal quality, low delay, and a high message delivery rate between nodes. These metrics are of utmostimportance for guaranteeing the quality of service in systems involving mobile UAV networks. UAV interaction approaches (e.g., [6]) denote a fixed point \(P\) to which the UAVs should fly in order to meet each other, to fly within communication range, so that they can share and update data to perform their tasks. Other approaches aimed at buffering and exchanging messages only during the occurrence of events-of-interest [7] or, alternatively, within predefined time intervals [8; 9]. These approaches consider pre-determined activities before the mission, so message exchange is severely affected in the absence of a communication signal (or when the signal quality is poor). In these works, dynamic evaluations are lacking of the communication spectrum to which each UAV node is submitted. Other researchers applied the repositioning of nodes in the occurrence of a detected target [10; 11]. For example, in [11], when an UAV from the fleet detects a target, it sends messages to the other UAVs, requesting them to reposition themselves at fixed distance intervals from it. However, other application scenarios cannot cope with trajectory modifications, e.g., on SAR missions that have tight timing restrictions [2; 12]. The use of different interfaces or communication protocols in the same network (heterogeneous networks) may be an interesting solution to maintain reliable communication links in networks composed of mobile nodes, given the vast number of successful cases in other mobile networks. Examples are the mobile ad hoc networks (MANET) and the vehicular ad hoc networks (VANET) [13; 14]. As shown in previous experiments [15], even supposedly similar interfaces such as IEEE 802.11n and 802.11p behave quite differently depending on the medium conditions. These interfaces have been widely used by researchers, who have applied their standard stack layers to develop solutions for improving UAV network reliability and stability in different mission applications [10; 11; 16]. The 802.11n became popular in the constitution of FANETs because it provides robust MAC and PHY layers that apply multiple input and multiple output (MIMO) technologies with high throughput and larger bandwidth, features that have been extensively explored in this scenario [4; 5]. Another important factor is that IEEE 802.11n is commonly found in UAVs classified as common commercial devices (low cost). IEEE 802.11p 5 GHz was developed for high-mobility networks or dynamic time-varying environments (i.e., networks composed of vehicles [14], underwater nodes [17], and robot nodes [18]). Given this context, this paper presents a communication interface manager (IM) for missions involving multiple UAVs.