Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hybrid Beamforming for Massive MIMO - A Survey   Hybrid multiple-antenna transceivers, which combine large-dimensional analog
pre/postprocessing with lower-dimensional digital processing, are the most
promising approach for reducing the hardware cost and training overhead in
massive MIMO systems. This paper provides a comprehensive survey of the various
incarnations of such structures that have been proposed in the literature. We
provide a taxonomy in terms of the required channel state information (CSI),
namely whether the processing adapts to the instantaneous or the average
(second-order) CSI; while the former provides somewhat better signal-to-noise
and interference ratio (SNIR), the latter has much lower overhead for CSI
acquisition. We furthermore distinguish hardware structures of different
complexities. Finally, we point out the special design aspects for operation at
millimeter-wave frequencies.

11
The categories of this paper are: hep-lat
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
34
The categories of this paper are: chem-ph
19
The categories of this paper are: eess
23
The categories of this paper are: solv-int
25
The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
21
The categories of this paper are: adap-org
24
The categories of this paper are: dg-ga
33
The categories of this paper are: plasm-ph
4
The categories of this paper are: cond-mat
26
The categories of this paper are: bayes-an
16
The categories of this paper are: stat
17
The categories of this paper are: q-fin
3
The categories of this paper are: physics