Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Sky High 5G: New Radio for Air-to-Ground Communications   Today, mobile operators are starting to deploy Fifth-Generation (5G) networks
to expand the coverage ubiquity of broadband wireless service. In contrast,
in-flight connectivity remains limited and its quality of service does not
always meet the expectations. Embracing 5G New Radio (NR) in Air-to-Ground
(A2G) communication systems can help narrow the gap between airborne and ground
connectivity. In this article, we focus on 5G NR based direct A2G
communications. We first provide an overview of the existing A2G systems which
are based on earlier generations of mobile technologies. Then we confirm the
feasibility of NR A2G systems with a performance study in a range of bands from
below 7 GHz to millimeter wave frequencies. The results show that NR A2G
systems can provide significantly improved data rates for in-flight
connectivity. We also identify the major challenges associated with NR A2G
communications, discuss enhancements to counteract the challenges, and point
out fruitful avenues for future research.

29
The categories of this paper are: funct-an
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
20
The categories of this paper are: acc-phys
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
13
The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th
17
The categories of this paper are: q-fin
16
The categories of this paper are: stat
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
12
The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph
31
The categories of this paper are: ao-sci