Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Reliable Beamspace Channel Estimation for Millimeter-Wave Massive MIMO
  Systems with Lens Antenna Array
19
The categories of this paper are: eess
27
The categories of this paper are: comp-gas
22
The categories of this paper are: chao-dyn
15
The categories of this paper are: nucl-ex
6
The categories of this paper are: astro-ph
32
The categories of this paper are: atom-ph
13
The categories of this paper are: quant-ph
5
The categories of this paper are: gr-qc
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
37
The categories of this paper are: supr-con
34
The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
26
The categories of this paper are: bayes-an