## 6 Findings and Future Work  
In this paper, we investigated the radio propagation characteristics of mmWave UAV BSs for the construction of temporary network areas during contingencies such as large-scale events and disasters, based on both numerical evaluations and demonstrative experiments. We evaluated the distance and coverage characteristics between access UAVs and terminals and analyzed the effect of radio interference due to earth reflection. Our findings revealed that our experimental devices, utilizing the IEEE802.11 ad standard, could achieve high-capacity communication at a rate of nearly 1.5 Gbps. Also, ground reflections were confirmed as sources of interference. Furthermore, the consistency across the three sets of evaluation results underscores the trustworthiness of our measurements. Consequently, the theoretical model we established is a valuable reference for subsequent model-driven inquiries in system design.  
However, since there is still a small gap between the measurement and theoretical results, our future endeavors will encompass more detailed investigations, e.g., to consider positional inaccuracies observed during the experiments. Given that our demonstrative experiment inherently operates in a three-dimensional (3D) space, our numerical evaluations require a more intricate 3D representation. For instance, accounting for potential shifts in the antenna's received polarization due to possible 3D beam misalignments is essential. Also, while our current study centered on access UAVs, an expanded focus is vital--encompassing backhaul UAVs and the broader mmWave UAV BS network--to comprehensively understand the radio propagation characteristics of our proposed system. The findings presented in this paper indicated that additional errors like positioning ones are likely to occur in real UAV-based networks that might degrade or improve the system's performance unexpectedly. It reconfirms the importance of experiment-based performance evaluation of a system like in this paper, rather than only computer-based theoretical work. Also, this paper indicates the significance of considering practical parameters in realistic environments when designing a UAV-based network that might involve many UAVs rather than only several UAVs like in this paper. One of our future works will include detailed investigation of the PHY/MAC conversion factor \(\alpha\). In addition, this experiment was conducted with a limited amount of data due to battery issues and the need for a license to fly drones in Japan. In future verification experiments, we will devise ways to secure a larger amount of data so that not only throughput but also other KPIs, e.g., delays, can be measured.  
Conceptualization, G.K.T.; methodology, R.M.; software, R.M.; validation, G.K.T., R.M. and J.N.; formal analysis, G.K.T., R.M. and J.N.; investigation, G.K.T., R.M. and J.N.; resources, G.K.T. and K.S.; data creation, R.M.; writing--original draft preparation, R.M.; writing--review and editing, G.K.T., R.M., J.N. and K.S.; visualization, R.M.; supervision, G.K.T., J.N. and K.S.; project administration, G.K.T. and J.N.; funding acquisition, G.K.T. and J.N. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the Strategic Information and Communications R&D Promotion Programme (SCOPE) by the Ministry of Internal Affairs and Communications, Japan (receipt number JP235003015).  
The data presented in this study are available in this article.  
We would like to express our sincere gratitude to all the individuals and organizations that have contributed to the publication of this work. We would especially like to thank [PERSON], who helped to conduct the experiments.  
The authors declare no conflicts of interest. The funders had no role in the design of this study; in the collection, analyses, experiments, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.