Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Analysis and Design of Secure Massive MIMO Systems in the Presence of
  Hardware Impairments   To keep the hardware costs of future communications systems manageable, the
use of low-cost hardware components is desirable. This is particularly true for
the emerging massive multiple-input multiple-output (MIMO) systems which equip
base stations (BSs) with a large number of antenna elements. However, low-cost
transceiver designs will further accentuate the hardware impairments which are
present in any practical communication system. In this paper, we investigate
the impact of hardware impairments on the secrecy performance of downlink
massive MIMO systems in the presence of a passive multiple-antenna
eavesdropper. Thereby, for the BS and the legitimate users, the joint effects
of multiplicative phase noise, additive distortion noise, and amplified
receiver noise are taken into account, whereas the eavesdropper is assumed to
employ ideal hardware. We derive a lower bound for the ergodic secrecy rate of
a given user when matched filter (MF) data precoding and artificial noise (AN)
transmission are employed at the BS. Based on the derived analytical
expression, we investigate the impact of the various system parameters on the
secrecy rate and optimize both the pilot sets used for uplink training and the
AN precoding. Our analytical and simulation results reveal that 1) the additive
distortion noise at the BS may be beneficial for the secrecy performance,
especially if the power assigned for AN emission is not sufficient; 2) all
other hardware impairments have a negative impact on the secrecy performance;
3) {\textcolor{blue}{despite their susceptibility to pilot interference in the
presence of phase noise}}, so-called spatially orthogonal pilot sequences are
preferable unless the phase noise is very strong; 4) the proposed generalized
null-space (NS) AN precoding method can efficiently mitigate the negative
effects of phase noise.

17
The categories of this paper are: q-fin
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
6
The categories of this paper are: astro-ph
11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph
4
The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn
16
The categories of this paper are: stat
29
The categories of this paper are: funct-an
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas