Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Reconfigurable Intelligent Surface-Assisted Massive MIMO: Favorable
  Propagation, Channel Hardening, and Rank Deficiency   Massive multiple-input multiple-output (MIMO) and reconfigurable intelligent
surface (RIS) are two promising technologies for 5G-and-beyond wireless
networks, capable of providing large array gain and multiuser spatial
multiplexing. Without requiring additional frequency bands, those technologies
offer significant improvements in both spectral and energy efficiency by
simultaneously serving many users. The performance analysis of an RIS-assisted
Massive MIMO system as a function of the channel statistics relies heavily on
fundamental properties including favorable propagation, channel hardening, and
rank deficiency. The coexistence of both direct and indirect links results in
aggregated channels, whose properties are the main concerns of this lecture
note. For practical systems with a finite number of antennas and scattering
elements of the RIS, we evaluate the corresponding deterministic metrics with
Rayleigh fading channels as a typical example.

9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
14
The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph
0
The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
23
The categories of this paper are: solv-int
29
The categories of this paper are: funct-an
15
The categories of this paper are: nucl-ex
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
27
The categories of this paper are: comp-gas