Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Understanding UAV Cellular Communications: From Existing Networks to
  Massive MIMO
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
26
The categories of this paper are: bayes-an
32
The categories of this paper are: atom-ph
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
16
The categories of this paper are: stat
20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
5
The categories of this paper are: gr-qc
4
The categories of this paper are: cond-mat
9
The categories of this paper are: nlin