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Electronics
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Active or Passive Metasurface for Wireless Communications
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Active or Passive Metasurface for Wireless Communications

A special issue of Electronics (ISSN 2079-9292). This special issue belongs to the section "Microwave and Wireless Communications".

Deadline for manuscript submissions: 15 June 2024 | Viewed by 2756

Special Issue Editors

Dr. Sai Xu

E-Mail Website
Guest Editor
Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield S3 7HF, UK
Interests: microwave/RF QR code; IRS; Physical layer security
Dr. Chen Chen

E-Mail Website
Guest Editor
Department of Electrical Engineering and Electronics, University of Liverpool, Liverpool L7 3NY, UK
Interests: IRS; massive MIMO; millimeter wave; terahertz communications; wireless security; machine learning
Dr. Yu Yao

E-Mail Website
Guest Editor
School of Engineering and Informatics, University of Sussex, Brighton BN1 9RH, Sussex, UK
Interests: IRS; antenna design; programmable metasurface

Special Issue Information

Dear Colleagues,

Metasurfaces pervade wireless communications via their expressions in multiple-input multiple-output (MIMO), millimeter wave and terahertz, full-duplex, edge computing, non-orthogonal multiple access, cognitive radio, physical layer security, backscatter, simultaneous wireless information and power transfer (SWIPT), localization, etc. Depending on whether radio frequency (RF) chains are involved or not, metasurfaces can be divided into two categories: active and passive metasurfaces. Typical examples of the difference include passive intelligent reflection surface (IRS)/ reconfigurable intelligent surface (RIS) and active holographic metasurfaces. Currently, metasurfaces are primarily used to reconfigure wireless environments or to act as transceivers. Accompanying these applications, however, is the skyrocketing difficulty of hardware overheads, computational complexity, power consumption, interference management, etc. Conversely, the potential of metasurfaces remains effectively unrealized. New related technologies or applications deserve to be explored, such as microwave/ RF QR code, RF neural network, holographic imaging, etc.

As such, the objective of this Special Issue is to collect the main findings and results carried out by industry and academia in the context of active or passive metasurfaces, operating on the basis of real system development and validation as well as new theoretical insights into key problems. In particular, we solicit high-quality original research papers on the topic of active or passive metasurface applications across wireless networks. These may include,  but are not limited to, the following topics:

  • Transceiver design and channel modeling for holographic MIMO communications;
  • Applications of IRS or RIS;
  • Design and performance analysis of frequency selective surfaces;
  • Exploration of transmissive and reflective IRS;
  • Channel estimation technologies related to metasurfaces;
  • Backscatter communications and microwave/RF QR code;
  • Effect of metasurfaces on indoor communications;
  • Metasurface-enhanced wireless security;
  • Active or passive metasurfaces for millimeter wave and terahertz wireless communications;
  • Application related to space–air–ground integrated networks, internet of things (IoT) networks;smart cities, vehicular communications, healthcare and telemedicine;
  • Experimental investigation on active or passive metasurfaces;
  • Machine learning for metasurface-aided communications.

Dr. Sai Xu
Dr. Chen Chen
Dr. Yu Yao
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Electronics is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • metasurfaces
  • holographic MIMO
  • IRS
  • RIS

Published Papers (4 papers)

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15 pages, 564 KiB  
Article
Energy-Efficient Access Point Selection Scheme for Reconfigurable-Intelligent-Surface-Assisted Cell-Free Massive MIMO Systems
by Weiran Wang, Jiaqi Song and Jianguo Zhou
Electronics 2024, 13(7), 1397; https://doi.org/10.3390/electronics13071397 - 07 Apr 2024
Viewed by 469
Abstract
Reconfigurable intelligent surface (RIS)-assisted cell-free (CF) massive Multiple-Input Multiple-Output (MIMO) technology exhibits significant potential in enhancing the energy efficiency of 6G mobile communications. Nevertheless, recent studies suggest that both access points (APs) and RISs encounter challenges related to a high energy consumption during [...] Read more.
Reconfigurable intelligent surface (RIS)-assisted cell-free (CF) massive Multiple-Input Multiple-Output (MIMO) technology exhibits significant potential in enhancing the energy efficiency of 6G mobile communications. Nevertheless, recent studies suggest that both access points (APs) and RISs encounter challenges related to a high energy consumption during operation. To address this issue, strategies involving AP hibernation and RIS shut-off are proposed. Subsequently, an optimization problem is formulated to jointly optimize RISs, beamforming vectors, and AP selection with the aim of maximizing the energy efficiency (EE). Initially, the non-convex optimization problem for maximizing energy efficiency is decomposed into three sub-problems. These sub-problems are subsequently reformulated using fractional programming and variational programming techniques and then solved using the successive convex approximation (SCA) algorithm, Dinkelbach algorithm, and greedy algorithm, respectively. Subsequently, an alternate optimization algorithm based on block gradient descent is introduced to iteratively solve the four-variable optimization problem, thereby obtaining an approximate solution to the original problem. The simulation results demonstrate that the algorithm significantly reduces energy consumption. Specifically, compared to the scheme without the hibernation strategy, the energy efficiency (EE) is enhanced by 35%. Full article
(This article belongs to the Special Issue Active or Passive Metasurface for Wireless Communications)
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12 pages, 3172 KiB  
Article
A New 1 Bit Electronically Reconfigurable Transmitarray
by Zizhen Zheng, Wu Ren, Weiming Li and Zhenghui Xue
Electronics 2024, 13(7), 1383; https://doi.org/10.3390/electronics13071383 - 05 Apr 2024
Viewed by 719
Abstract
This article proposes a novel 1 bit electronically reconfigurable transmitarray, designed to facilitate digital two-dimensional beam scanning, boasting both high gain and a slim profile. The fundamental phase shifting unit of the transmitarray unit cell consists of a resonant cavity composed of a [...] Read more.
This article proposes a novel 1 bit electronically reconfigurable transmitarray, designed to facilitate digital two-dimensional beam scanning, boasting both high gain and a slim profile. The fundamental phase shifting unit of the transmitarray unit cell consists of a resonant cavity composed of a pair of orthogonal metal gates and dielectric layers, with a cross-sectional height of 0.17 λ. The middle layer of the phase-shifting unit is composed of circular gaps and C-shaped patches, and two diodes with opposite directions are loaded. By turning the diodes ON and OFF, current reversal is accomplished, allowing the unit to transition between its 0 and 1 states and achieve transmission-phase quantization. The unit’s minimal insertion loss is 0.37 dB in state 0 and 0.35 dB in state 1, respectively. In order to verify our design, we designed and processed a 16 × 16 transmitarray in the C-band. The simulated results are consistent with the experimental results. The experimental results show that the transmitarray can achieve ± 45° beam scanning on both the E-plane and H-plane, and the maximum gain is 20.59 dBi at 5 GHz, with an aperture efficiency of 20.5%. Full article
(This article belongs to the Special Issue Active or Passive Metasurface for Wireless Communications)
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13 pages, 2623 KiB  
Article
Sum-Rate Maximization Scheme for Multi-RIS-Assisted NOMA Uplink Systems
by Debao Qiu and Jianbo Ji
Electronics 2024, 13(5), 969; https://doi.org/10.3390/electronics13050969 - 03 Mar 2024
Viewed by 629
Abstract
Reconfigurable intelligent surface (RIS) and non-orthogonal multiple access (NOMA) are both highly promising technologies for future communication. Compared with traditional single-RIS-assisted NOMA systems, this paper considered multi-RIS-assisted NOMA uplink communication systems and proposed a sum-rate maximization scheme. At present, most research on RIS-assisted [...] Read more.
Reconfigurable intelligent surface (RIS) and non-orthogonal multiple access (NOMA) are both highly promising technologies for future communication. Compared with traditional single-RIS-assisted NOMA systems, this paper considered multi-RIS-assisted NOMA uplink communication systems and proposed a sum-rate maximization scheme. At present, most research on RIS-assisted NOMA systems has not considered the joint optimization of users’ power, multi-RIS deployment, and multi-RIS phase shifts. Firstly, this paper proposed a sum-rate problem with multiple variates, which are involved in users’ power, multi-RIS deployments, and multi-RIS phase shifts. This problem is usually very complex and non-convex, which makes it very difficult to obtain an optimal solution. Then, the original problem was decomposed into three sub-problems through several derivations, which are relatively simple and easy to solve. Finally, the optimal multi-RIS deployment locations were obtained by a simulated annealing particle-swarm optimization algorithm, and a suboptimal solution based on positive semidefinite relaxation was adopted to solve the joint optimization problem of users’ power and multi-RIS phase shifts, respectively. The research results indicate that the sum-rate for the considered systems with the multi-RIS optimization algorithm can be improved by about 1 bps/Hz, compared with that of non-optimization, and under the same total number of RIS reflection units as a single-RIS scheme, the performance of the proposed scheme in this paper is superior to the single-RIS scheme, which proves the effectiveness of the proposed algorithm. Full article
(This article belongs to the Special Issue Active or Passive Metasurface for Wireless Communications)
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13 pages, 433 KiB  
Article
IRS Backscatter-Based Secrecy Enhancement against Active Eavesdropping
by Yuanyuan Miao, Yu Shao and Jie Zhang
Electronics 2024, 13(2), 265; https://doi.org/10.3390/electronics13020265 - 06 Jan 2024
Viewed by 557
Abstract
This paper proposes to combat active eavesdropping using intelligent reflecting surface (IRS) backscatter techniques. To be specific, the source (Alice) sends the confidential information to the intended user (Bob), while the eavesdropper (Willie) transmits a jamming signal to interrupt the transmission for more [...] Read more.
This paper proposes to combat active eavesdropping using intelligent reflecting surface (IRS) backscatter techniques. To be specific, the source (Alice) sends the confidential information to the intended user (Bob), while the eavesdropper (Willie) transmits a jamming signal to interrupt the transmission for more data interception. To enhance the secrecy, an IRS is deployed and connected with Alice through fiber to transform the jamming signal into the confidential signal by employing backscatter techniques. Based on the considered model, an optimization problem is formulated to maximize the signal-to-interference-plus-noise ratio (SINR) at Bob under the constraints of the transmit power at Alice, the reflection vector at the IRS, and the allowable maximum the SINR at Willie. To address the optimization problem, an alternate optimization algorithm is developed. The simulation results verify the achievable secrecy gain of the proposed scheme. The proposed scheme is effective in combating active eavesdropping. Furthermore, the deployment of large-scale IRS significantly enhances the secrecy rate. Full article
(This article belongs to the Special Issue Active or Passive Metasurface for Wireless Communications)
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