166 research outputs found
Antenna Array Enabled Space/Air/Ground Communications and Networking for 6G
Antenna arrays have a long history of more than 100 years and have evolved
closely with the development of electronic and information technologies,
playing an indispensable role in wireless communications and radar. With the
rapid development of electronic and information technologies, the demand for
all-time, all-domain, and full-space network services has exploded, and new
communication requirements have been put forward on various space/air/ground
platforms. To meet the ever increasing requirements of the future sixth
generation (6G) wireless communications, such as high capacity, wide coverage,
low latency, and strong robustness, it is promising to employ different types
of antenna arrays with various beamforming technologies in space/air/ground
communication networks, bringing in advantages such as considerable antenna
gains, multiplexing gains, and diversity gains. However, enabling antenna array
for space/air/ground communication networks poses specific, distinctive and
tricky challenges, which has aroused extensive research attention. This paper
aims to overview the field of antenna array enabled space/air/ground
communications and networking. The technical potentials and challenges of
antenna array enabled space/air/ground communications and networking are
presented first. Subsequently, the antenna array structures and designs are
discussed. We then discuss various emerging technologies facilitated by antenna
arrays to meet the new communication requirements of space/air/ground
communication systems. Enabled by these emerging technologies, the distinct
characteristics, challenges, and solutions for space communications, airborne
communications, and ground communications are reviewed. Finally, we present
promising directions for future research in antenna array enabled
space/air/ground communications and networking
Opportunistic Wiretapping/Jamming: A New Attack Model in Millimeter-Wave Wireless Networks
While the millimeter-wave (mmWave) communication is robust against the
conventional wiretapping attack due to its short transmission range and
directivity, this paper proposes a new opportunistic wiretapping and jamming
(OWJ) attack model in mmWave wireless networks. With OWJ, an eavesdropper can
opportunistically conduct wiretapping or jamming to initiate a more hazardous
attack based on the instantaneous costs of wiretapping and jamming. We also
provide three realizations of the OWJ attack, which are mainly determined by
the cost models relevant to distance, path loss and received power,
respectively. To understand the impact of the new attack on mmWave network
security, we first develop novel approximation techniques to characterize the
irregular distributions of wiretappers, jammers and interferers under three OWJ
realizations. With the help of the results of node distributions, we then
derive analytical expressions for the secrecy transmission capacity to depict
the network security performance under OWJ. Finally, we provide extensive
numerical results to illustrate the effect of OWJ and to demonstrate that the
new attack can more significantly degrade the network security performance than
the pure wiretapping or jamming attack
Reducing Precoder/Channel Mismatch and Enhancing Secrecy in Practical MIMO Systems Using Artificial Signals
Practical multiple-input-multiple-output (MIMO) systems depend on a
predefined set of precoders to provide spatial multiplexing gain. This
limitation on the flexibility of the precoders affects the overall performance.
Here, we propose a transmission scheme that can reduce the effect of mismatch
between users' channels and precoders. The scheme uses the channel knowledge to
generate an artificial signal, which realigns the predefined precoder to the
actual channel. Moreover, the scheme can provide an additional level of secrecy
for the communication link. The performance of the proposed scheme is evaluated
using bit-error rate (BER), error vector magnitude (EVM), and secrecy capacity.
The results show a significant improvement for the legitimate user, along with
a degradation for the eavesdropper.Comment: 4 pages, 5 figures. Accepted for publication in IEEE Communications
Letter
A Tutorial on Extremely Large-Scale MIMO for 6G: Fundamentals, Signal Processing, and Applications
Extremely large-scale multiple-input-multiple-output (XL-MIMO), which offers
vast spatial degrees of freedom, has emerged as a potentially pivotal enabling
technology for the sixth generation (6G) of wireless mobile networks. With its
growing significance, both opportunities and challenges are concurrently
manifesting. This paper presents a comprehensive survey of research on XL-MIMO
wireless systems. In particular, we introduce four XL-MIMO hardware
architectures: uniform linear array (ULA)-based XL-MIMO, uniform planar array
(UPA)-based XL-MIMO utilizing either patch antennas or point antennas, and
continuous aperture (CAP)-based XL-MIMO. We comprehensively analyze and discuss
their characteristics and interrelationships. Following this, we examine exact
and approximate near-field channel models for XL-MIMO. Given the distinct
electromagnetic properties of near-field communications, we present a range of
channel models to demonstrate the benefits of XL-MIMO. We further motivate and
discuss low-complexity signal processing schemes to promote the practical
implementation of XL-MIMO. Furthermore, we explore the interplay between
XL-MIMO and other emergent 6G technologies. Finally, we outline several
compelling research directions for future XL-MIMO wireless communication
systems.Comment: 38 pages, 10 figure
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