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Ayass et al. Intell Robot 2022;2(1):20-36 https://dx.doi.org/10.20517/ir.2021.07 Page 22

2. FLYING AD HOC NETWORK
Ad hoc networks, referred to by the IETF (Internet Engineering Task Force) as MANET (mobile ad hoc
networks), have as their main characteristic the fact that they do not have infrastructure. As a result, all their
functions must be performed by the devices. Thus, the devices that make up an ad hoc network must be
[1]
able to communicate with each other acting as routers .

Ad hoc networks are often used in scenarios where there is a need to quickly set up a network, usually
where there is no proper infrastructure. The devices can move arbitrarily, unpredictably modifying the
network topology, which requires a permanent adaptation and reconfiguration of routes so that the devices
can still communicate with each other.

In the new context of fifth-generation networks (5G), a derivation of the ad hoc networks called FANET has
emerged. FANETs are ad hoc networks composed of remotely controlled flying devices (UAVs) that
[2]
communicate with each other . Due to the flexibility, versatility, and even easy operation of FANETs, they
are used for both military and civil applications, for example plantation control in agriculture, forest
clearing, and city security (see Figure 1).

In recent years, because of technological advances in areas such as robotics, telecommunications, and
computer networks, UAVs have emerged as alternatives in civil and military areas, providing several
applications. Thus, UAVs are intended to improve or create a network infrastructure in places that are
difficult to access, such as natural disaster areas or enemy territories. With this, FANET appears as an
acceptable solution in this new context, allowing the collection of information in a flexible, fast, and reliable
way.

One of the goals of FANETs is to create a cooperative network, using multiple UAVs to cover an area that
cannot be covered by a single UAV. Thus, it is possible to create an aerial mesh network in which its devices
(drones) communicate and transmit information with each other. Therefore, it is necessary to have reliable
and stable communication between devices to maintain good levels of quality of service/quality of
experience (QoS/QoE).

In FANETs, the mobility index is much higher than a traditional ad hoc network, leading to frequent
topology changes. This is the reason FANETs must be self-configuring and self-organizing. Such a network
must be prepared for sudden changes in its topology, organization, and even communication.

The mobility of UAVs and their spatial location are also very important for determining communication
routes. With the motion, these routes are usually remade to continue with the interconnection of the UAVs.
For this reason, routing must be done dynamically, and the routing protocol must be efficient and simple,
increasing the autonomy of the UAVs and reducing the delay in data delivery between the drones.

UAVs are responsible for overflying the environment. They have sensors to collect information and can
establish communication with each other more easily by finding fewer obstacles in their line of sight,
reducing the number of UAVs needed to cover a certain area. However, weather conditions can impair
communication due to wind, rain, and other factors.

FANETs have a high computational power. Thus, they have a greater capacity for transmitting information
since in many cases they are responsible for transmitting information in real time (with videos from the
monitored environment). Thus far, there are no specific routing protocols for FANETs. Traditional