# NFV/SDN as an Enabler for Dynamic Placement Method of mmWave Embedded UAV Access Base Stations
## 6 Conclusions  
In this paper, we investigated the use of access UAV networks to provide data to disaster areas where ground base stations have been shut down due to disasters. In this paper, we reported our proposed placement method and frequency division method of \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Carrier Frequency & 2 [GHz] \\ Bandwidth & 20 [MHz] \\ EIRP & 36 [dBm] \\ Beam Width & 45 [degrees] \\ Receive Antenna Gain & 0 [dBi] \\ Temperature & 298 [K] \\ Environmental Constant (\(\alpha,\beta,\gamma\)) [37] & 0.3, 500 [km\({}^{-2}\)], 15 [m] \\ Excessive Loss (\(\eta_{\text{LoS}}\), \(\eta_{\text{NLG}}\)) & 0.8 [dB], 19 [dB] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Microwave band parameters. Figure 11: Methods’ comparison with microwaves. access UAVs in the UAV network and indicated that NFV/SDN technologies are key enablers for such dynamic construction of the proposed networks. For static users, the introduction of the minimum inclusive circle problem to the K-means method improved the offered data rate by 50% compared to the conventional method without the K-means method, and by 17% compared to the conventional method using only the K-means method. As for the frequency division method, when the frequency was divided for each UAV, the average offered data rate decreased by 28% while the data rate of users with a 5% outage increased by 124%. However, by using the method of introducing FFR into the UAV network, the average offered data rate was improved by 1% while it was improved by 101% for users with a 5% outage. When the method used in this study was applied to microwaves, the performance was improved by 0.4% compared to the conventional method. In contrast, the performance of this method for millimeter-wave applications was improved by 16.3%, indicating that this method provides better results at higher frequencies. In summary, this paper proposed an effective placement method and frequency division algorithm for millimeter-wave UAV cellular networks considering a realistic distribution of users where hotspots exist, differentiating our work from previous studies. Numerical results confirmed the effectiveness of the proposed method, in terms of not only average user rate but also outage user rate. Investigation of the algorithm against more realistic scenarios is our ongoing work. For example, [45] dealt with a dynamic user distribution where UEs have mobility. In the future, we will also consider the placement method in realistic environments with shadowing and joint optimization together with the backhaul UAVs. In addition, although this paper presented our fundamental theoretical studies, we have been constructing a Proof-of-Concept system using actual experimental equipment and conducted real-life outdoor experiments. Preliminary experimental results had been published in [46], where we demonstrated the feasibility of millimeter-wave access of a single UAV. Via the experiment, we found out there were many natural/artificial attributes that may affect the performance of UAV networks in real life. Our ongoing work is to overcome these difficulties and demonstrate the proposed UAV system as a whole via SDN/NFV enablers. Conceptualization, G.K.T., M.O., and J.N. ; methodology, M.O. ; writing--original draft preparation, M.O., G.K.T., and J.N. ; data curation, M.O. ; funding acquisition, G.K.T. All authors have read and agreed to the published version of the manuscript. This research received no external funding. We would like to thank the anonymous reviewers for their careful reading of our manuscript and their many insightful comments and suggestions to improve the quality of the manuscript. We would also like to acknowledge the Telecommunications Advancement Foundation for its financial support to complete part of this research. The authors declare no conflict of interest.