# Non-Terrestrial Networks with UAVs: A Projection on Flying Ad-Hoc Networks
## 4 State-of-the-Art FANET
### Standards for FANETs  
In the last decade, there has been an extensive effort to envision the FANET and industrialize it. As a result of the benefits provided by FANET and to take economic advantage of it, 3 GPP approved to support FANET integration into the 5G ecosystem [61,70]. In Release 16 [62], 3 GPP accepted the first study item on NR to support FANET. The goal was to investigate channel models (propagation conditions and mobility), establish deployment scenarios and related system parameters, and identify any important effect areas that may require more research. Similarly, the Institute of Electrical and Electronics Engineers (IEEE) and ITU have made some efforts towards FANET standardization. In IEEE P1936.1 [71], IEEE proposed a standard framework for FANET applications. In IEEE P1939.1 [72], structuring of UAV operations in FANET was standardized. In IEEE P1920.1 [73], communications and networking standards were clarified. ITU also shed light on the FANET architectural standardization in ITU-T Y.UAV.arch [74] and ITU-T F.749.10 [75] and provided communication requirements for UAV-based services. Following these standardization pathways, in [36], communication protocols were considered a general issue of FANETs. In [15], adaptive communication protocols were proposed based on position-prediction and reinforcement self-learning routing techniques. The beauty of this work was the capability of developing communications with respect to the modifications happening in the FANET topology. In [76], a joint sensing and communication protocol [77] was proposed that enables the FANET to be integrated within the cellular networks. It was also proposed to use non-orthogonal multiple access (NOMA) where several UAVs/nodes can access radio resources non-orthogonally to reduce the latency and improve the spectral efficiency. Moreover, [58] indicated three main aspects of FANETs to support UAVs operations in different applications. They were: (i) dependable 3D wireless access with integrated cellular networks and FANETs, (ii) AI at the edge UAVs for signal/image processing and smart decision makings, and (iii) effective control and inter-UAV communications for cooperative activities. In addition, an integration between FANET and the cellular networks was proposed to provide strong connection, dependability, security, and safety to UAVs by using their sophisticated features and UAS traffic management (UTM) (UTM's goal is to provide the reliable transportation of products and services through UAS/FANET [78]) supports. On the other hand, the studies in [21; 67; 79; 80] proposed aeronautical channel models for air-to-air (A2A), air-to-ground (A2G) and ground-to-air (G2A) communications in cellular FANETs, as shown in Figure 6. [PERSON] and [PERSON] in [81] further investigated communication standards for FANETs in terms of remote identification of UAVs, command and control communications, radio access network (RAN) support, and various solutions to the issue of RF interference during cellular UAVs integration. They also discussed FANET node registration and wireless service requirements. To conclude, although a wide variety of short- and long-range technologies, given in [61; 62; 71; 72; 73; 74; 75; 76; 77; 78], can be helpful in FANETs for specific applications, the communication framework standardization of FANETs is an ongoing direction with an essential need for significant experimentation platforms to bridge the gap between basic research, stan  
Figure 6: Advancements of FANET are mainly in communication standards, physical layer characterization of data transfers, role & trajectory management of UAVs, and data packet routing. Communications can be classified into three classes of A2A, A2G, and G2A. Based on the network design, each UAV may have four main roles of relay, carrier, forwarder, master. The Master UAV is responsible for the network management as a core. dardization, optimization, and deployment as well as existing and future use cases and research difficulties.