Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: When Is the Achievable Rate Region Convex in Two-User Massive MIMO
  Systems?   This letter investigates the achievable rate region in Massive
multiple-input-multiple-output (MIMO) systems with two users, with focus on the
i.i.d.~Rayleigh fading and line-of-sight (LoS) scenarios. If the rate region is
convex, spatial multiplexing is preferable to orthogonal scheduling, while the
opposite is true for non-convex regions. We prove that the uplink and downlink
rate regions with i.i.d.~Rayleigh fading are convex, while the convexity in LoS
depends on parameters such as angular user separation, number of antennas, and
signal-to-noise ratio (SNR).

28
The categories of this paper are: alg-geom
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
11
The categories of this paper are: hep-lat
23
The categories of this paper are: solv-int
34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys
32
The categories of this paper are: atom-ph
5
The categories of this paper are: gr-qc
15
The categories of this paper are: nucl-ex
29
The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
16
The categories of this paper are: stat
19
The categories of this paper are: eess