112 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
The Road to Next-Generation Multiple Access: A 50-Year Tutorial Review
The evolution of wireless communications has been significantly influenced by
remarkable advancements in multiple access (MA) technologies over the past five
decades, shaping the landscape of modern connectivity. Within this context, a
comprehensive tutorial review is presented, focusing on representative MA
techniques developed over the past 50 years. The following areas are explored:
i) The foundational principles and information-theoretic capacity limits of
power-domain non-orthogonal multiple access (NOMA) are characterized, along
with its extension to multiple-input multiple-output (MIMO)-NOMA. ii) Several
MA transmission schemes exploiting the spatial domain are investigated,
encompassing both conventional space-division multiple access (SDMA)/MIMO-NOMA
systems and near-field MA systems utilizing spherical-wave propagation models.
iii) The application of NOMA to integrated sensing and communications (ISAC)
systems is studied. This includes an introduction to typical NOMA-based
downlink/uplink ISAC frameworks, followed by an evaluation of their performance
limits using a mutual information (MI)-based analytical framework. iv) Major
issues and research opportunities associated with the integration of MA with
other emerging technologies are identified to facilitate MA in next-generation
networks, i.e., next-generation multiple access (NGMA). Throughout the paper,
promising directions are highlighted to inspire future research endeavors in
the realm of MA and NGMA.Comment: 43 pages, 38 figures; Submitted to Proceedings of the IEE
Role of Reconfigurable Intelligent Surfaces in 6G Radio Localization: Recent Developments, Opportunities, Challenges, and Applications
Reconfigurable intelligent surfaces (RISs) are seen as a key enabler low-cost
and energy-efficient technology for 6G radio communication and localization. In
this paper, we aim to provide a comprehensive overview of the current research
progress on the RIS technology in radio localization for 6G. Particularly, we
discuss the RIS-assisted radio localization taxonomy and review the studies of
RIS-assisted radio localization for different network scenarios, bands of
transmission, deployment environments, as well as near-field operations. Based
on this review, we highlight the future research directions, associated
technical challenges, real-world applications, and limitations of RIS-assisted
radio localization
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