# Three-Dimensional Drone Cell Placement: Drone Placement for Optimal Coverage
## 1 Introduction
All these products and trials show that the future of terrestrial RANs in 5G communication will be mainly supported by aerial methods with support provided by DCs. Although some products were not as successful or beneficial as others leading to their early termination, the future of DA-RANs is brighter than ever. Multiple DA-RAN architectures have been proposed by pioneers in the field based on the advantages of DA-RANs. The two most important DA-RAN architectures based on previous work in the field according to the types of DC used can be classified as the small DC DA-RAN and the macro DC DA-RAN. In the case of a small DC DA-RAN, the network architecture is similar to Cloud-RAN (C-RAN) where each DC exchanges data with its respective connected BS; in a small DC DA-RAN, the Remote Radio Heads (RRHs) are replaced with DCs [21]. Each BS acts as the main controller that can deploy and allocate DCs in DAs. Users in each DA in turn connect to these DCs and connect to the BS by the signal relay between the DC and BS. Small DCs are meant to act as an aerial extension of the BS, and hence, are not needed to support or have the full functionality of a terrestrial BS. This ensures that the power consumption of the DC is kept in check, and due to having a smaller payload and device weight, a small DC can operate for a longer period of time. The relatively small coverage of a small DC in comparison to a macro DC helps keep the inter-drone interference to a minimum, and coupled with its fast deployment capabilities, it has proven to be a suitable and reliable choice for enhancing future RAN and DA-RAN architecture by improving network coverage and signal strength in DAs [22]. A macro DC DA-RAN acts as an independent aerial RAN architecture flying over terrestrial RANs. Macro DCs usually have the full functionality of a terrestrial BS and provide additional spectrum resources to mitigate the inefficiency of the available spectrum and enhance the connectivity of connected users and devices. Macro DCs require a large amount of energy consumption due to being a fully operational BS, and they also support a much larger coverage when compared to terrestrial BSs. Researchers have since proposed many architectures leveraging both macro DCs and small DCs together for providing services, and their efficiency is evident in [23], where FSO wireless links are leveraged for communication networks. This work mainly focuses on the use of small DC-DA-RAN architecture. One of the most critical parts of the small DC-DA-RAN communication model is its limited range and power, which calls for an efficient usage of DCs. Like terrestrial networks, DCs are subjected to many factors that dictate the QoS of the DA-RAN architecture. Free space path loss, signal reflection and blocking due to natural or artificial obstructions are some of the reasons [24]. As such, the optimal placement of DCs has been the main focus for many researchers to achieve a high QoS. In this work, a concise overview of the DA-RAN's functionality is presented in Section 2, followed by the system model in Section 3 and the implemented methods in Section 4. Lastly, Section 5 covers a series of experiments conducted using the base algorithm parameters, which sparked further exploration into algorithmic diversity and parameter tuning, culminating in an analysis of the resulting trade-offs.