Smart Radio Environments Empowered by Reconfigurable Intelligent Surfaces: How It Works, State of Research, and The Road Ahead

By M. Di Renzo, Alessio Zappone, Merouane Debbah, Mohamed-Slim Alouini, Chau Yuen, J. de Rosny, Sergei A. Tretyakov. IEEE Journal on Selected Areas in Communications, 2020

1,415 citations recorded by the source corpus.

Reconfigurable intelligent surfaces (RISs) are an emerging transmission technology for application to wireless communications. RISs can be realized in different ways, which include (i) large arrays of inexpensive antennas that are usually spaced half of the wavelength apart; and (ii) metamaterial-based planar or conformal large surfaces whose scattering elements have sizes and inter-distances much smaller than the wavelength. Compared with other transmission technologies, e.g., phased arrays, multi-antenna transmitters, and relays, RISs require the largest number of scattering elements, but each of them needs to be backed by the fewest and least costly components. Also, no power amplifiers are usually needed. For these reasons, RISs constitute a promising software-defined architecture that can be realized at reduced cost, size, weight, and power (C-SWaP design), and are regarded as an enabling technology for realizing the emerging concept of smart radio environments (SREs). In this paper, we (i) introduce the emerging research field of RIS-empowered SREs; (ii) overview the most suitable applications of RISs in wireless networks; (iii) present an electromagnetic-based communication-theoretic framework for analyzing and optimizing metamaterial-based RISs; (iv) provide a comprehensive overview of the current state of research; and (v) discuss the most important research issues to tackle. Owing to the interdisciplinary essence of RIS-empowered SREs, finally, we put forth the need of reconciling and reuniting C. E. Shannon’s mathematical theory of communication with G. Green’s and J. C. Maxwell’s mathematical theories of electromagnetism for appropriately modeling, analyzing, optimizing, and deploying future wireless networks empowered by RISs.

Subfields: Aerospace Engineering, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/3367a26b0a3c68a2eee12858311dc945e6aba853

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Citations in the corpus

Active RIS Versus Passive RIS: Which is Superior With the Same Power Budget? (2021, background): “Passive reconﬁgurable intelligent surface (RIS)-aided systems have attracted extensive research attention recently [1]– [5].”
Edge Artificial Intelligence for 6G: Vision, Enabling Technologies, and Applications (2021, background): “The beneﬁts of RIS-empowered FL systems highly depend on the capabilities of manipulating electromagnetic waves at the metasurfaces [49], whose reconﬁgurability is typically enabled by switches, tunable material, topological metasur-faces, and hybrid metasurfaces [299].”
A Tutorial on Environment-Aware Communications via Channel Knowledge Map for 6G (2023, background): “The above discussions reveal that for both pilot-based channel training and beam sweeping methods, from the link perspective, the required training overhead increases with the channel dimensions.”
Active Reconfigurable Intelligent Surface-Aided Wireless Communications (2021, methodology): “To cater for variable wireless environment, some necessary control and switch circuits are deployed at RIS, enabling each RE to recon-ﬁgure its reﬂection coefﬁcient accordingly [4].”
Reconfigurable Intelligent Surfaces for 6G Systems: Principles, Applications, and Research Directions (2021, positive): “Hence, compared to conventional active transmitters, RISs can operate with much lower cost in terms of hardware and power consumption [2], [6].”
Path Loss Modeling and Measurements for Reconfigurable Intelligent Surfaces in the Millimeter-Wave Frequency Band (2021, background): “In recent years, reconﬁgurable intelligent surfaces (RISs) have emerged as a promising enabling technology for 6G networks [3]–[7].”
6G Internet of Things: A Comprehensive Survey (2021, background): “THz communications are envisioned as a driving technology for 6G-IoT which requires 100+ Gbps data rates and 1-millisecond latency.”
An Overview of Signal Processing Techniques for RIS/IRS-Aided Wireless Systems (2021, neutral): “If the RIS is deployed at high-frequency bands, such as mmwave/sub-THz, the Fraunhofer distance also increases due to the smaller wavelength [236]– [238].”
Reconfigurable Intelligent Surfaces: Principles and Opportunities (2020, background): “Further information and details can be found in [7] and [64].”
What Will the Future of UAV Cellular Communications Be? A Flight From 5G to 6G (2021, background): “An RIS can realize sophisticated and exotic signal transformations, which include anomalous refractions, polarization conversion, collimation, and focusing [186].”