# Developing an Intelligent Cellular Structure Design for a UAV Wireless Communication Topology
## 2 Related Studies  
This section presents representative related research works that have been described in the literature, where a set of criteria has been utilized to review this related research work that meets the research scope. The criteria are as follows: (a) UAV platform type, (b) network topology, (c) AI framework, and (d) cellular design. This section concludes by highlighting research gaps and our own research motivations. Wireless communication systems can be divided roughly into two main types, namely terrestrial systems (e.g., base stations) and aerial-based systems (e.g., Satellite and UAVs). Each system has its own advantages and shortcomings [9]. Despite the advancements of both systems, they are not without limitations due to their nature and/or technological capabilities [10]. Terrestrial systems suffer from limited frequency bands and bandwidth, multipath constraints, being vulnerable to dis-connectivity in the case of natural disasters, limited coverage footprint, and high cost to deploy, especially in rough terrains (e.g., mountains) [11]. Satellites suffer from a noticeable propagation path loss and delay, complexity of manufacturing, launching, maintenance, tracking and handover, lifetime variations, and environmental damage resulting from gas emissions during launch [12]. Thus, UAVs, including High Altitude Platforms (HAPs), Low Altitude Platforms (LAPs), Tethered Balloons and Drones, are considered as a midway solution [13]. They exhibit deployment flexibility, providing last-mile connectivity, reconfigurability, and wide  
Figure 1: Representative examples of IoE-enabled UAV applications. footprint coverage with LoS advantages [14]. Moreover, providing wireless communication services via UAVs is increasingly seen as an innovative solution that could offer many of the satellite benefits, but without the distance penalty [15]. Such a suitable alternative infrastructure could serve a wide range of applications and services, e.g., telecommunications, search and rescue, remote sensing, surveillance and security, smart cities, smart agriculture, monitoring disaster-relief activities, atmospheric studies, smart service delivery, border monitoring, high-resolution aerial imaging, smart journalism, localization, and navigation [16]. Researchers are striving to develop various aspects related to UAV state-of-the-art usages, applications, and capabilities [17]. UAVs can take advantage of many advanced technologies, such as D2D communication, small cells (e.g., Femtocell), (HetNet) Network, Multiple Input Multiple Output (MIMO) antennas, Worldwide Interoperability for Microwave Access (WiMAX) [18], and Wireless Fidelity (WiFi) (e.g., 802.11 AX (WiFi 6e)) linked to 5G and 6G [19]. Figure 2 demonstrates representative projects of different aerial platforms across the globe, including Airships, Tethered Balloons, Aircrafts, and Drones. This reflects the great international efforts that have been put into the development of these aerial platform technologies [20]. The rest of this section highlights the recent related work on cellular structure design. This section concludes by highlighting research gaps and our own research motivations, as Table 1 shows. At 20 km altitude using a HAP platform, researchers in [21] focus on multi-cell design using an adaptive smart antenna array to serve fixed users. Authors in [22] present a Neural Networks (NN) framework via a LAP to enhance wireless connectivity. The optimized model dealt with a fixed cellular structure design to guarantee both received signal strength and low transmission power. Figure 2: Aerial platform examples across the globe. (**a**) Google Loon—International, (**b**) HAA—USA, (**c**) ABSOLUTE Tethered Balloon—EU, (**d**) KARI—Korean, (**e**) Facebook fixed-wing Aircraft—International, (**f**) PSATRI Drone—KSA. A tethered drone is used in [23] to guarantee a good level of energy and data. The drone can float within the designated region to find an optimal transmission location that maximizes the cellular coverage for ground users.