  The use of unmanned aerial vehicle (UAV)-based communication in
millimeter-wave (mmWave) frequencies to provide on-demand radio access is a
promising approach to improve capacity and coverage in beyond-5G (B5G) systems.
There are several design aspects to be addressed when optimizing for the
deployment of such UAV base stations. As traffic demand of mobile users varies
across time and space, dynamic algorithms that correspondingly adjust the UAV
locations are essential to maximize performance. In addition to careful
tracking of spatio-temporal user/traffic activity, such optimization needs to
account for realistic backhaul constraints. In this work, we first review the
latest 3GPP activities behind integrated access and backhaul system design,
support for UAV base stations, and mmWave radio relaying functionality. We then
compare static and mobile UAV-based communication options under practical
assumptions on the mmWave system layout, mobility and clusterization of users,
antenna array geometry, and dynamic backhauling. We demonstrate that leveraging
the UAV mobility to serve moving users may improve the overall system
performance even in the presence of backhaul capacity limitations.
