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.

通过使用无线电波的无人机进行通信以提高容量和覆盖范围，在优化无人机基站的部署时需要考虑多个方面，最重要的是动态算法和现实的回程限制等。本文比较了在 millimeter-wave 系统布局，用户动态、用户聚类、天线阵列几何以及动态回传的实际情况下的静态和移动无人机通信选项，发现即使在回程容量限制的情况下，利用无人机移动为移动用户提供服务也可以提高整个系统的性能。

mmWave B5G 系统中的空中接入与回传：性能动态与优化

Aerial Access and Backhaul in mmWave B5G Systems: Performance Dynamics  and Optimization

Large antenna arrays and millimeter-wave (mmWave) frequencies have been
attracting growing attention as possible candidates to meet the high
requirements of future 5G mobile networks. In view of the large path loss
attenuation in these bands, beamforming techniques that create a beam in the
direction of the user equipment are essential to perform the transmission. For
this purpose, in this paper, we aim at characterizing realistic antenna
radiation patterns, motivated by the need to properly capture mmWave
propagation behaviors and understand the achievable performance in 5G cellular
scenarios. In particular, we highlight how the performance changes with the
radiation pattern used. Consequently, we conclude that it is crucial to use an
accurate and realistic radiation model for proper performance assessment and
system dimensioning.

本文探讨了大型天线阵列和毫米波频率作为 5G 移动网络的潜在备选方案的问题。针对这些频段中的大路径损耗衰减，作者提出了旨在刻画现实中天线辐射模式的目的，并通过突出强调性能如何随着所用辐射模式的不同而变化，得出了需要用准确、实际的辐射模型进行适当的性能评估和系统设计结论。

5G 毫米波通信场景中逼真天线模式研究

Study of Realistic Antenna Patterns in 5G mmWave Cellular Scenarios

Hybrid multiple-antenna transceivers, which combine large-dimensional analog
pre/postprocessing with lower-dimensional digital processing, are the most
promising approach for reducing the hardware cost and training overhead in
massive MIMO systems. This paper provides a comprehensive survey of the various
incarnations of such structures that have been proposed in the literature. We
provide a taxonomy in terms of the required channel state information (CSI),
namely whether the processing adapts to the instantaneous or the average
(second-order) CSI; while the former provides somewhat better signal-to-noise
and interference ratio (SNIR), the latter has much lower overhead for CSI
acquisition. We furthermore distinguish hardware structures of different
complexities. Finally, we point out the special design aspects for operation at
millimeter-wave frequencies.

本文综述了现有文献中提出的混合多天线收发机结构的各种形式，提出了在信道状态信息方面的分类，介绍了在毫米波频段操作的特殊设计方面的问题。