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The adoption of a Reconfigurable Intelligent Surface (RIS) for downlink multi-user communication from a multi-antenna base station is investigated in this paper. We develop energy-efficient designs for both the transmit power allocation and…

Information Theory · Computer Science 2022-06-23 Chongwen Huang , Alessio Zappone , George C. Alexandropoulos , Mérouane Debbah , Chau Yuen

The concept of fluid reconfigurable intelligent surface (FRIS) upgrades the conventional reconfigurable intelligent surface (RIS) paradigm by empowering its reflecting elements with positioning reconfigurability. This letter aims to…

Information Theory · Computer Science 2025-11-21 Xusheng Zhu , Kai-Kit Wong , Boyi Tang , Wen Chen , Chan-Byoung Chae

Reconfigurable intelligent surface (RIS)-aided near-field communications is investigated. First, the necessity of investigating RIS-aided near-field communications and the advantages brought about by the unique spherical-wave-based…

Information Theory · Computer Science 2024-03-05 Xidong Mu , Jiaqi Xu , Yuanwei Liu , Lajos Hanzo

Reconfigurable intelligent surface (RIS) is a promising technology to enhance the spectral and energy efficiency in a wireless communication system. The design of the phase shifts of an RIS in every channel coherence interval demands a huge…

Signal Processing · Electrical Eng. & Systems 2024-05-15 Sadaf Syed , Dominik Semmler , Donia Ben Amor , Michael Joham , Wolfgang Utschick

Reconfigurable intelligent surfaces (RISs) are one of the most promising technological enablers of the next (6th) generation of wireless systems. In this paper, we introduce a novel use-case of the RIS technology in radio localization,…

Signal Processing · Electrical Eng. & Systems 2022-02-24 Kamran Keykhosravi , Gonzalo Seco-Granados , George C. Alexandropoulos , Henk Wymeersch

Active reconfigurable intelligent surface (RIS) emerges as an effective technique to resist the double-fading attenuation of passive RIS. By embedding with power harvesting function, it further evolves to zero-power active RIS, which can…

Information Theory · Computer Science 2025-10-17 Xiao Zheng , Wenchi Cheng , Jingqing Wang , Zhuohui Yao , Jiangzhou Wang

The advantages of millimeter-wave and large antenna arrays technologies for accurate wireless localization received extensive attentions recently. However, how to further improve the accuracy of wireless localization, even in the case of…

Information Theory · Computer Science 2020-09-17 Yiming Liu , Erwu Liu , Rui Wang

Millimeter-wave (mmWave) positioning has emerged as a promising technology for next-generation intelligent systems. The advent of reconfigurable intelligent surfaces (RISs) has revolutionized high-precision mmWave localization by enabling…

Signal Processing · Electrical Eng. & Systems 2026-04-23 Xin Cheng , Yuqing Yang , Guangjie Han , Menglu Li , Ruoguang Li , Feng Shu

Localization using multiple base stations (BSs) has gained much attention for its advantage in localization accuracy. However, the performance of the multi-BS system suffers from its limited number of antennas. To solve the above issue, we…

Signal Processing · Electrical Eng. & Systems 2025-07-23 Weiqiao Zhu , Mengyuan Cao , Yang Yang , Haobo Zhang , Weijun Hao , Xiaofei Jia , Hongliang Zhang

Reconfigurable intelligent surfaces (RIS) can be crucial in next-generation communication systems. However, designing the {RIS} phases according to the instantaneous channel state information (CSI) can be challenging in practice due to the…

Information Theory · Computer Science 2023-09-26 Athira Subhash , Abla Kammoun , Ahmed Elzanaty , Sheetal Kalyani , Yazan H. Al-Badarneh , Mohamed-Slim Alouini

Reconfigurable intelligent surfaces (RIS), recognized as a critical enabler for 6G networks, exhibit unprecedented capabilities in electromagnetic wave manipulation and wireless channel reconfiguration. By leveraging existing network…

Information Theory · Computer Science 2025-08-19 Wenjun Teng , Weicong Chen , Yiping Zuo , Wankai Tang , Shi Jin

While Reconfigurable Intelligent Surfaces (RISs) constitute one of the most prominent enablers for the upcoming sixth Generation (6G) of wireless networks, the design of efficient RIS phase profiles remains a notorious challenge when large…

Signal Processing · Electrical Eng. & Systems 2024-07-19 Kyriakos Stylianopoulos , Panagiotis Gavriilidis , George C. Alexandropoulos

As 6G wireless networks seek to enable robust and dynamic programmable wireless environments (PWEs), reconfigurable intelligent surfaces (RISs) have emerged as a cornerstone for controlling electromagnetic wave propagation. However,…

This paper presents a 1-bit reconfigurable intelligent surface (RIS) fabricated using a three-layer structure. It employs a manual layer stackup incorporating an optimal air gap to reduce the effective dielectric losses while using a…

Systems and Control · Electrical Eng. & Systems 2026-04-07 Mahendra Kheti , Debapratim Ghosh , Soumya P. Dash

Reconfigurable intelligent surfaces (RISs) have the potential to enable user localization in scenarios where traditional approaches fail. Building on prior work in single-antenna RIS-enabled localization, we investigate the potential to…

Signal Processing · Electrical Eng. & Systems 2021-09-27 Moustafa Rahal , Benoit Denis , Kamran Keykhosravi , Bernard Uguen , Henk Wymeersch

Reconfigurable intelligent surfaces (RISs) bring various benefits to the current and upcoming wireless networks, including enhanced spectrum and energy efficiency, soft handover, transmission reliability, and even localization accuracy.…

Signal Processing · Electrical Eng. & Systems 2023-10-03 Jiguang He , Aymen Fakhreddine , Arthur S. de Sena , Yu Tian , Merouane Debbah

This paper explores distributed Reconfigurable Intelligent Surfaces (RISs) by introducing a cooperative dimension that enhances adaptability and performance. It focuses on strategically deploying multiple RISs to improve connectivity with…

Signal Processing · Electrical Eng. & Systems 2024-11-13 Youssef Hussein , Mohamad Assaad , Thierry Clessienne

The concept of reconfigurable intelligent surface (RIS) has been proposed to change the propagation of electromagnetic waves, e.g., reflection, diffraction, and refraction. To accomplish this goal, the phase values of the discrete RIS units…

Signal Processing · Electrical Eng. & Systems 2019-11-11 Jiguang He , Henk Wymeersch , Tachporn Sanguanpuak , Olli Silvén , Markku Juntti

Reconfigurable intelligent surface (RIS) is a newly-emerged technology that might fundamentally change how wireless networks are operated. Though extensively studied in recent years, the practical limitations of RIS are often neglected when…

Signal Processing · Electrical Eng. & Systems 2023-12-12 Parisa Ramezani , Yasaman Khorsandmanesh , Emil Björnson

Smart radio environments aided by reconfigurable intelligent reflecting surfaces (RIS) have attracted much research attention recently. We propose a joint optimization strategy for beamforming, RIS phases, and power allocation to maximize…

Information Theory · Computer Science 2022-08-02 Athira Subhash , Abla Kammoun , Ahmed Elzanaty , Sheetal Kalyani , Yazan H. Al-Badarneh , Mohamed-Slim Alouini