Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Wireless Communications with Unmanned Aerial Vehicles: Opportunities and
  Challenges   Wireless communication systems that include unmanned aerial vehicles (UAVs)
promise to provide cost-effective wireless connectivity for devices without
infrastructure coverage. Compared to terrestrial communications or those based
on high-altitude platforms (HAPs), on-demand wireless systems with low-altitude
UAVs are in general faster to deploy, more flexibly re-configured, and are
likely to have better communication channels due to the presence of short-range
line-of-sight (LoS) links. However, the utilization of highly mobile and
energy-constrained UAVs for wireless communications also introduces many new
challenges. In this article, we provide an overview of UAV-aided wireless
communications, by introducing the basic networking architecture and main
channel characteristics, highlighting the key design considerations as well as
the new opportunities to be exploited.

5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an
23
The categories of this paper are: solv-int
10
The categories of this paper are: q-bio
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
12
The categories of this paper are: nucl-th
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg
15
The categories of this paper are: nucl-ex
13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
22
The categories of this paper are: chao-dyn
24
The categories of this paper are: dg-ga
19
The categories of this paper are: eess