mmWave bands are highly linear and are significantly attenuated by obstacles. Since this architecture utilizes drones, it is possible to communicate in the upper airspace area with good communication visibility without being affected by obstructions. In addition, since there has been little use of communications in the sky area and mmWave band radio waves have not been used much, it is possible to communicate with little radio interference. Currently, mobile BS vehicles are used for temporary network construction during emergencies, but drones can cover a wider area because they communicate from a higher altitude [34]. In the future, satellite communications such as \"Starlink\" and UAV-based communication technologies such as HAPS (High Altitude Platform Systems) are expected to be used for communications from the sky [33; 35] at the altitude of about 20 km. On the other hand, the drones in this paper will be used at altitudes of tens to hundreds of meters so that the communication distance will be relatively short, the atmospheric loss will be smaller than others, and communication will be possible with low latency. In the past, network construction utilizing UAV BSs had been considered by other researchers, but only microwaves had been used to guarantee connectivity [36]. Microwaves have limited applicability due to bandwidth limitations. There is also concern about the depletion of frequency resources, necessitating new research on frequency sharing and the development of higher frequency bands. Although there have been studies on building UAV-based networks using mmWave technology, these have been limited to theoretical studies based on simulations [37; 38]. The main features of 5G communication services include high-capacity communications, large numbers of simultaneous connections, low latency, and high reliability [39]. In [40], latency in mmWave networks was studied. The goal there was to construct an edge content delivery system that adapts to user information and relocate content servers through dynamic routing on a mmWave mesh backhaul network, and experiments were conducted to study its effectiveness. The latency in the paper was measured through ping tests. Since mmWave communications are significantly affected by distance attenuation and shielding, the placement of UAVs concerning user distribution is an important issue [33]. In [33], dynamic placement of access UAVs for mmWave UAV BSs for user distribution was considered. Here, assuming that the user distribution is known in advance, the authors proposed a method of UAV placement by frequency division to maximize the system rate. Here, the method in [41] was used to determine the optimal altitude of the UAVs, while the K-means method and the minimum circle problem were employed to determine the UAVs' optimal interference-reduced placement. The paper also showed that frequency division efficiently distributes the available bandwidth to each UAV, which helps to avoid interference and improves the overall system rate. In mmWave UAV BSs, many UAVs communicate with each other, but the communication from the UAVs to the user is directed toward the ground, which causes ground reflection. Therefore, to realize a simultaneous uplink/downlink UAV network, it is nec  
Figure 1: Overview of system architecture [33]. essary to consider ground-reflected wave interference between adjacent UAVs. For this purpose [42], employed SIR (Signal Interference Power Ration) as a metric to show that an architecture with circularly polarized antennas can significantly reduce interference compared to the conventional architecture with linearly polarized antennas. Furthermore, it was found that interference can be significantly reduced when both backhaul UAVs and access UAVs use identical circularly polarized antennas. In addition to the above, power consumption is also an issue in mmWave UAV BS networks. Although specifications for wired drones have been considered, the operating range of UAVs is limited by the power cable length [43; 44].