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Reconfigurable intelligent surface (RIS) has been widely discussed as new technology to improve wireless communication performance. Based on the unique design of RIS, its elements can reflect, refract, absorb, or focus the incoming waves…

Signal Processing · Electrical Eng. & Systems 2020-09-03 Salah Eddine Zegrar , Liza Afeef , Huseyin Arslan

This paper provides a theoretical framework for understanding the performance of reconfigurable intelligent surface (RIS)-aided massive multiple-input multiple-output (MIMO) with zero-forcing (ZF) detectors under imperfect channel state…

Information Theory · Computer Science 2021-11-03 Kangda Zhi , Cunhua Pan , Gui Zhou , Hong Ren , Maged Elkashlan , Robert Schober

Channel acquisition is one of the main challenges for the deployment of reconfigurable intelligent surface (RIS) aided communication systems. This is because an RIS has a large number of reflective elements, which are passive devices with…

Signal Processing · Electrical Eng. & Systems 2023-02-16 Jie Chen , Ying-Chang Liang , Hei Victor Cheng , Wei Yu

This letter investigates the channel estimation problem in THz wireless communications where a RIS is employed to assist wireless transmission between different devices. Unlike existing studies, we consider a novel scenario where specific…

Signal Processing · Electrical Eng. & Systems 2026-03-30 Wen-Xuan Long , Marco Moretti , Giacomo Bacci , Luca Sanguinetti

Fluid reconfigurable intelligent surfaces (FRISs) have recently emerged as a promising paradigm for wireless communications, wherein the reflecting elements can dynamically select their effective radiating positions from a dense preset…

Signal Processing · Electrical Eng. & Systems 2026-05-19 Amarilton L. Magalhães , André L. F. de Almeida , George C. Alexandropoulos

Beyond Diagonal Reconfigurable Intelligent Surfaces (BD-RIS) has emerged as a promising evolution of RIS technology. By enabling interconnections between RIS elements, BD-RIS architectures offer greater flexibility in wave manipulation…

Signal Processing · Electrical Eng. & Systems 2025-12-08 Kangchun Zhao , Yijie Mao

Reconfigurable intelligent surfaces (RISs) have emerged as a promising technology to enhance the performance of sixth-generation (6G) and beyond communication systems. The passive nature of RISs and their large number of reflecting elements…

Information Theory · Computer Science 2024-06-12 Nipuni Ginige , Arthur Sousa de Sena , Nurul Huda Mahmood , Nandana Rajatheva , Matti Latva-aho

In this paper, we investigate channel estimation for a large intelligent surface (LIS) aided multiple-input multiple-output (MIMO) communication system. Due to the close proximity of communication devices and LIS terminal, the desired…

Information Theory · Computer Science 2020-06-02 Jawad Mirza , Bakhtiar Ali

Considering the dimensionality of a typical reconfigurable intelligent surface (RIS), channel state information acquisition in RIS-assisted systems requires lengthy pilot transmissions. Moreover, the large aperture of the RIS may cause…

Signal Processing · Electrical Eng. & Systems 2023-12-27 Mehdi Haghshenas , Parisa Ramezani , Maurizio Magarini , Emil Björnson

Cell-Free Massive multiple-input multiple-output (MIMO) and reconfigurable intelligent surface (RIS) are two promising technologies for application to beyond-5G networks. This paper considers Cell-Free Massive MIMO systems with the…

Information Theory · Computer Science 2021-12-20 Trinh Van Chien , Hien Quoc Ngo , Symeon Chatzinotas , Marco Di Renzo , Björn Ottersten

Reconfigurable intelligent surfaces (RISs) are considered as potential technologies for the upcoming sixth-generation (6G) wireless communication system. Various benefits brought by deploying one or multiple RISs include increased spectrum…

Signal Processing · Electrical Eng. & Systems 2021-04-16 Jiguang He , Nhan Thanh Nguyen , Rafaela Schroeder , Visa Tapio , Joonas Kokkoniemi , Markku Juntti

Channel estimation is one of the key challenges for the deployment of extremely large-scale reconfigurable intelligent surface (XL-RIS) assisted multiple-input multiple-output (MIMO) systems. In this paper, we study the channel estimation…

Signal Processing · Electrical Eng. & Systems 2024-04-29 Jeongjae Lee , Hyeongjin Chung , Yunseong Cho , Sunwoo Kim , Songnam Hong

Reconfigurable intelligent surfaces (RISs) are one of the foremost technological enablers of future wireless systems. They improve communication and localization by providing a strong non-line-of-sight path to the receiver. In this paper,…

Signal Processing · Electrical Eng. & Systems 2022-04-26 Kamran Keykhosravi , Henk Wymeersch

Simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS)-aided cell-free massive multiple-input multiple-output (CF-mMIMO) systems are investigated under spatially correlated fading channels using realistic…

Information Theory · Computer Science 2025-01-06 Zeping Sui , Hien Quoc Ngo , Michail Matthaiou , Lajos Hanzo

Reconfigurable intelligent surfaces (RISs) have been proposed recently as new technology to tune the wireless propagation channels in real-time. However, most of the current works assume single-RIS (S-RIS)-aided systems, which can be…

Signal Processing · Electrical Eng. & Systems 2021-09-21 Khaled Ardah , Sepideh Gherekhloo , André L. F. de Almeida , Martin Haardt

This paper presents a physics-based channel modeling and optimization framework for reconfigurable intelligent surface (RIS)-assisted downlink multi-user multiple-input single-output (MU-MISO) communication systems in site-specific…

Signal Processing · Electrical Eng. & Systems 2026-03-24 Ziqi Liu , Wei Yu , Sean Victor Hum

We study channel estimation for a beyond diagonal reconfigurable intelligent surface (BD-RIS) aided multiple input single output system. We first describe the channel estimation strategy based on the least square (LS) method, derive the…

Signal Processing · Electrical Eng. & Systems 2024-05-27 Hongyu Li , Yumeng Zhang , Bruno Clerckx

In this paper, we investigate cascaded channel estimation for reconfigurable intelligent surface (RIS)-aided millimeter-wave multi-user communication systems. Since the complex channel gains of the cascaded RIS channel are generally…

Signal Processing · Electrical Eng. & Systems 2025-10-21 Gyoseung Lee , Junil Choi

We consider a bidirectional in-band full-duplex (FD) multiple-input multiple-output (MIMO) system subject to imperfect channel state information (CSI), hardware distortion, and limited analog cancellation capability as well as the…

Signal Processing · Electrical Eng. & Systems 2020-06-09 Hiroki Iimori , Giuseppe Thadeu Freitas de Abreu , Koji Ishibashi

Flexible Intelligent Metasurfaces (FIMs) enable wireless systems to adapt their three-dimensional geometry through morphing, thereby providing new spatial degrees of freedom. However, continuous deformation complicates the accurate…

Signal Processing · Electrical Eng. & Systems 2026-05-29 Vinícius L. Romano , André L. F. de Almeida , Daniel C. Araújo