# IoT and UAV Integration in 5G Hybrid Terrestrial-Satellite Networks
## 5 IoT, UAVs, and Satellites in the Emerging 5G Technology
### IoT, UAV/Satellite, and 5G Integration  
The integration between UAVs/satellites and the 5G terrestrial network with the aim to support the IoT use case can be achieved in different ways and leads to manifold benefits depending, as said above, on the role of non-terrestrial objects. UAVs and satellites can be employed in 5G application scenarios in case there is no other communication infrastructure, with the aim to collect and forward the generated data by IoT devices. UAVs can help extend the coverage of commercial IoT networks, previously mentioned in Section 2, by acting as mobile access points whose position and movement path can be properly set and dynamically adjusted. A possible first step for the integration of the aforementioned technologies is discussed in the following. Some preliminaries before presenting the different architectures are given:* IoT devices may be equipped to be 5G UE. The drawback is that IoT devices are in most cases very simple objects whose size, hardware, and available resource constraints are very strict. Hosting 5G UE functionalities may be an excessive burden. * UAVs can act as 5G UE, 5G-gNBs, or as transparent Relay Nodes (RNs). In the first option, UAVs communicate with the IoT devices through a wireless non-5G interface, e.g., one of the commercial or standardized LPWA solutions shown in Tables 1 and 2. UAVs may be linked to a 5G cell generated by a satellite in visibility (5G-gNB on-board satellite) or get access to the 5G Core Network (CN) through a satellite acting as RN. In the second case, UAVs equipped to be 5G-gNBs allow the deployment of 5G cells on-demand and offer connectivity to devices equipped as 5G-UE. Concerning the third option, if the IoT devices are 5G-UE and the access to the 5G network takes place in the terrestrial segment, UAVs are \"RNs transparent\" to the 5G communication and only implement frequency conversion and radio frequency amplification to allow data transmission to the satellite. * Satellites can act as 5G-gNBs if they are equipped with a regenerative payload or as RNs between 5G UE and 5G RAN if they are transparent payload satellites. The same considerations can be applied for the satellite gateways, which can act as 5G-gNBs or be linked to 5G-gNBs through terrestrial links. * The terrestrial segment includes 5G CN and 5G gNBs (if they are not deployed elsewhere). Figures Figures 2-7 show the possible network architecture configurations (from the user plane viewpoint), taking into account the 5G standardization progress for the non-terrestrial network reported in [47]. In detail, the choice of considering IoT devices as not 5G-oriented devices is depicted in Figures 2-4. They are equipped with interfaces based on an IoT protocol stack such as the ones described in Section 2. In this case, the UAV acts as 5G-UE, taking charge of the conversion between IoT and the 5G protocol stacks. The difference among these architectures is in the role of the satellite, i.e., in the location of the 5G-gNB. In Figure 2, the satellite is a simple RN, an \"extender\", whose only aim is to perform Radio Frequency processing and Frequency Switching (RF and FS) required to transmit from the UAV to the satellite link and vice versa. 5G-gNB is located on the ground close to the 5G-CN and the satellite link 5G-UE and 5G-gNB. In Figure 3, the satellite is still a simple RN, but 5G-gNB is located closer to 5G-UE. 5G-gNB is still located on the ground, and the satellite acts as a backhaul between 5G-gNB and 5G-CN. The main difference between architectures in Figures 2 and 3 is that, in the latter case, 5G-gNB is located close to the edge of the network, easing the employment of technologies, such as MEC, and allowing a better interaction between 5G-UE and 5G-gNB due to the lower communication delay between them. In Figure 4, the 5G-gNB functionality is moved on-board the satellite, increasing its complexity and leading to additional challenges the 3 GPP is studying [48].