# IoT and UAV Integration in 5G Hybrid Terrestrial-Satellite Networks
## 1 Introduction  
The evolution of the telecommunication networks, which will lead the world to the Fifth Generation of Mobile Communications (5G), is characterized by a deep change in the telecommunication network infrastructure and in the employed technologies. 5G will have to support a higher number of users/devices requiring an Internet connectivity with different performance requirements and a higher number of applications and use cases. The Internet of Things (IoT) is one of these recently-emerging use cases, which will involve an even higher number of connected devices aimed at collecting and sending data with different purposes and over different application scenarios, such as smart city, smart factory, and smart agriculture. In some cases, the terrestrial infrastructure is not enough to guarantee the typical 5G Key Performance Indicators (KPIs) due to its design and intrinsic limitations. Coverage is an example: the terrestrial infrastructure will never be able to cover certain areas, such as oceans and rural and remote ares where there is no chance of or economic advantage in building a terrestrial network such as the one in big cities. Resilience in case of temporary or permanent infrastructure unavailability is another key point. Flying technologies, such as communication satellites and Unmanned Aerial Vehicles (UAVs), can contribute to overcome the limitations of the terrestrial infrastructure, offering wider coverage, higher resilience and availability, and improving user's Quality of Experience (QoE). IoT can benefit from the UAVs and satellite integration in the 5G ecosystem in many ways, also beyond the coverage extension and the increase of the available bandwidth that these objects can offer. UAVs and, perhaps in the future, satellites may be an essential part of the service. UAVs have been used in various sectors of our daily lives, allowing us to perform activities ranging from package delivery such as Prime Air from Amazon [1] to diving in water as done by the Boeing's drone that can be transformed into a submarine [2]. For the IoT, they can be properly equipped to act as IoT gateways, collecting and forwarding data from IoT sensors located in the covered area to the authorized users connected to the Internet through the 5G network. Their position and their movement path can be arbitrarily set depending on how the IoT devices are distributed in the area to cover and on the amount and periodicity of the generated data, offering a customizable solution, also reducing the infrastructure cost. Besides, depending on the payload hardware, they can also act as intermediate nodes for multiple IoT solutions, offering a multi-technology IoT solution in a single node. Communications satellites have been widely employed to extend the communications (telephony and Internet) throughout the world since almost fifty years ago. Currently, there are tens of satellite communication constellations with this purpose, and some others are planned to be deployed to offer global Internet connectivity through Low Earth Orbit (LEO) satellites [3; 4]. Some preliminary studies already focused on the exploitation of satellite networks for the IoT, envisioning the data exchange between IoT devices and end users through satellite communications [5]. Satellites can act as intermediate nodes directly connecting to the IoT devices or through other intermediate collecting nodes (such as UAVs) in order to offer a dynamically-deployable real-time connectivity. Within this context, this paper considers the impact of and need for the IoT environment, the role of UAVs and satellites, and the joint integration of these technologies in the future 5G. The paper is structured as follows, Section 2 gives a detailed description about the main IoT solutions, both short and long range, commercial and standardized solutions, highlighting the differences among them and presenting their network infrastructure.