402 research outputs found
IRS-assisted UAV Communications: A Comprehensive Review
Intelligent reflecting surface (IRS) can smartly adjust the wavefronts in
terms of phase, frequency, amplitude and polarization via passive reflections
and without any need of radio frequency (RF) chains. It is envisaged as an
emerging technology which can change wireless communication to improve both
energy and spectrum efficiencies with low energy consumption and low cost. It
can intelligently configure the wireless channels through a massive number of
cost effective passive reflecting elements to improve the system performance.
Similarly, unmanned aerial vehicle (UAV) communication has gained a viable
attention due to flexible deployment, high mobility and ease of integration
with several technologies. However, UAV communication is prone to security
issues and obstructions in real-time applications. Recently, it is foreseen
that UAV and IRS both can integrate together to attain unparalleled
capabilities in difficult scenarios. Both technologies can ensure improved
performance through proactively altering the wireless propagation using smart
signal reflections and maneuver control in three dimensional (3D) space. IRS
can be integrated in both aerial and terrene environments to reap the benefits
of smart reflections. This study briefly discusses UAV communication, IRS and
focuses on IRS-assisted UAC communications. It surveys the existing literature
on this emerging research topic and highlights several promising technologies
which can be implemented in IRS-assisted UAV communication. This study also
presents several application scenarios and open research challenges. This study
goes one step further to elaborate research opportunities to design and
optimize wireless systems with low energy footprint and at low cost. Finally,
we shed some light on future research aspects for IRS-assisted UAV
communication
RIS-Assisted Coverage Enhancement in Millimeter-Wave Cellular Networks
The use of millimeter-wave (mmWave) bandwidth is one key enabler to achieve
the high data rates in the fifth-generation (5G) cellular systems. However,
mmWave signals suffer from significant path loss due to high directivity and
sensitivity to blockages, limiting its adoption within small-scale deployments.
To enhance the coverage of mmWave communication in 5G and beyond, it is
promising to deploy a large number of reconfigurable intelligent surfaces
(RISs) that passively reflect mmWave signals towards desired directions. With
this motivation, in this work we study the coverage of an RIS-assisted
large-scale mmWave cellular network using stochastic geometry, and derive the
peak reflection power expression of an RIS and the downlink
signal-to-interference ratio (SIR) coverage expression in closed forms. These
analytic results clarify the effectiveness of deploying RISs in the mmWave SIR
coverage enhancement, while unveiling the major role of the density ratio
between active base stations (BSs) and passive RISs. Furthermore, the results
show that deploying passive reflectors is as effective as equipping BSs with
more active antennas in the mmWave coverage enhancement. Simulation results
confirm the tightness of the closed form expressions, corroborating our major
findings based on the derived expressions.Comment: Accepted in IEEE ACCESS, Copyright (c) 2015 IEEE. Personal use of
this material is permitted. However, permission to use this material for any
other purposes must be obtained from the IEEE by sending a request to
[email protected]
Reconfigurable Intelligent Surfaces for Smart Cities: Research Challenges and Opportunities
The concept of Smart Cities has been introduced as a way to benefit from the
digitization of various ecosystems at a city level. To support this concept,
future communication networks need to be carefully designed with respect to the
city infrastructure and utilization of resources. Recently, the idea of 'smart'
environment, which takes advantage of the infrastructure for better performance
of wireless networks, has been proposed. This idea is aligned with the recent
advances in design of reconfigurable intelligent surfaces (RISs), which are
planar structures with the capability to reflect impinging electromagnetic
waves toward preferred directions. Thus, RISs are expected to provide the
necessary flexibility for the design of the 'smart' communication environment,
which can be optimally shaped to enable cost- and energy-efficient signal
transmissions where needed. Upon deployment of RISs, the ecosystem of the Smart
Cities would become even more controllable and adaptable, which would
subsequently ease the implementation of future communication networks in urban
areas and boost the interconnection among private households and public
services. In this paper, we describe our vision of the application of RISs in
future Smart Cities. In particular, the research challenges and opportunities
are addressed. The contribution paves the road to a systematic design of
RIS-assisted communication networks for Smart Cities in the years to come.Comment: Submitted for possible publication in IEEE Open Journal of the
Communications Societ
Reconfigurable Intelligent Surface for Physical Layer Security in 6G-IoT: Designs, Issues, and Advances
Sixth-generation (6G) networks pose substantial security risks because
confidential information is transmitted over wireless channels with a broadcast
nature, and various attack vectors emerge. Physical layer security (PLS)
exploits the dynamic characteristics of wireless environments to provide secure
communications, while reconfigurable intelligent surfaces (RISs) can facilitate
PLS by controlling wireless transmissions. With RIS-aided PLS, a lightweight
security solution can be designed for low-end Internet of Things (IoT) devices,
depending on the design scenario and communication objective. This article
discusses RIS-aided PLS designs for 6G-IoT networks against eavesdropping and
jamming attacks. The theoretical background and literature review of RIS-aided
PLS are discussed, and design solutions related to resource allocation,
beamforming, artificial noise, and cooperative communication are presented. We
provide simulation results to show the effectiveness of RIS in terms of PLS. In
addition, we examine the research issues and possible solutions for RIS
modeling, channel modeling and estimation, optimization, and machine learning.
Finally, we discuss recent advances, including STAR-RIS and malicious RIS.Comment: Accepted for IEEE Internet of Things Journa
Synergizing Airborne Non-Terrestrial Networks and Reconfigurable Intelligent Surfaces-Aided 6G IoT
On the one hand, Reconfigurable Intelligent Surfaces (RISs) emerge as a
promising solution to meet the demand for higher data rates, improved coverage,
and efficient spectrum utilization. On the other hand, Non-Terrestrial Networks
(NTNs) offer unprecedented possibilities for global connectivity. Moreover, the
NTN can also support the upsurge in the number of Internet of Things (IoT)
devices by providing reliable and ubiquitous connectivity. Although NTNs have
shown promising results, there are several challenges associated with their
usage, such as signal propagation delays, interference, security, etc. In this
article, we have discussed the possibilities of integrating RIS with an NTN
platform to overcome the issues associated with NTN. Furthermore, through
experimental validation, we have demonstrated that the RIS-assisted NTN can
play a pivotal role in improving the performance of the entire communication
system.Comment: 15 pages, 5 figure
Passive Reflection Codebook Design for IRS-Integrated Access Point
Intelligent reflecting surface (IRS) has emerged as a promising technique to
extend the wireless signal coverage of access point (AP) and improve the
communication performance cost-effectively. In order to reduce the path-loss of
the cascaded user-IRS-AP channels, the IRS-integrated AP architecture has been
proposed to deploy the IRSs and the antenna array of the AP within the same
antenna radome. To reduce the pilot overhead for estimating all IRS-involved
channels, in this paper, we propose a novel codebook-based IRS reflection
design for the IRS-integrated AP to enhance the coverage performance in a given
area. In particular, the codebook consisting of a small number of codewords is
designed offline by employing an efficient sector division strategy based on
the azimuth angle. To ensure the performance of each sector, we optimize its
corresponding codeword for IRS reflection pattern to maximize the
sector-min-average-effective-channel-power (SMAECP) by applying the alternating
optimization (AO) and semidefinite relaxation (SDR) methods. With the designed
codebook, the AP performs the IRS reflection training by sequentially applying
all codewords and selects the one achieving the best communication performance
for data transmission. Numerical results show that our proposed codebook design
can enhance the average channel power of the whole coverage area, as compared
to the system without IRS. Moreover, our proposed codebook-based IRS reflection
design is shown to achieve significant performance gain over other benchmark
schemes in both single-user and multi-user transmissions.Comment: 13 pages, 11 figure
- …