Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Pilot Contamination Mitigation for Wideband Massive MMO: Number of Cells
  Vs Multipath
17
The categories of this paper are: q-fin
18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph
13
The categories of this paper are: quant-ph
29
The categories of this paper are: funct-an
24
The categories of this paper are: dg-ga
9
The categories of this paper are: nlin
22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
23
The categories of this paper are: solv-int
16
The categories of this paper are: stat
5
The categories of this paper are: gr-qc