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The concept of a large intelligent surface (LIS) has recently emerged as a promising wireless communication paradigm that can exploit the entire surface of man-made structures for transmitting and receiving information. An LIS is expected…

Information Theory · Computer Science 2019-12-30 Minchae Jung , Walid Saad , Youngrok Jang , Gyuyeol Kong , Sooyong Choi

Reconfigurable intelligent surfaces (RISs) consist of many passive elements of metamaterials whose impedance can be controllable to change the characteristics of wireless signals impinging on them. Channel estimation is a critical task when…

Information Theory · Computer Science 2023-09-14 Özlem Tuğfe Demir , Emil Björnson

This paper studies a reconfigurable intelligent surface (RIS)-assisted cell-free massive multiple-input multiple-output (CF-mMIMO) system with multiple RISs. Joint design of transmit precoding, RIS coefficients, and receive combining is…

Signal Processing · Electrical Eng. & Systems 2025-10-21 Navid Reyhanian , Reza Ghaderi Zefreh , Parisa Ramezani , Emil Bjornson

We introduce a novel deep reinforcement learning (DRL) approach to jointly optimize transmit beamforming and reconfigurable intelligent surface (RIS) phase shifts in a multiuser multiple input single output (MU-MISO) system to maximize the…

Networking and Internet Architecture · Computer Science 2023-03-30 Baturay Saglam , Doga Gurgunoglu , Suleyman S. Kozat

A wireless communication system is studied that operates in the presence of multiple reconfigurable intelligent surfaces (RISs). In particular, a multi-operator environment is considered where each operator utilizes an RIS to enhance its…

Information Theory · Computer Science 2024-03-04 Nikolaos I. Miridakis , Theodoros A. Tsiftsis , Panagiotis A. Karkazis , Helen C. Leligou , Petar Popovski

Large intelligent surfaces (LISs) constitute a new and promising wireless communication paradigm that relies on the integration of a massive number of antenna elements over the entire surfaces of man-made structures. The LIS concept…

Information Theory · Computer Science 2021-01-29 Minchae Jung , Walid Saad , Gyuyeol Kong

Sensing-assisted communication schemes have recently garnered significant research attention. In this work, we design a dual-function reconfigurable intelligent surface (RIS), integrating both active and passive elements, referred to as the…

Signal Processing · Electrical Eng. & Systems 2025-08-14 Cheng Luo , Luping Xiang , Jie Hu , Kun Yang

In this paper, a single user multiple input single output downlink wireless communication system is investigated, in which multiple reconfigurable intelligent surfaces (RISs) are deployed to improve the propagation condition. Our objective…

Signal Processing · Electrical Eng. & Systems 2019-12-24 Huayan Guo , Ying-Chang Liang , Sa Xiao

Large intelligent surfaces (LISs) have been recently proposed as an effective wireless communication solution that can leverage antenna arrays deployed on the entirety of man-made structures such as walls. An LIS can provide space-intensive…

Information Theory · Computer Science 2019-08-27 Minchae Jung , Walid Saad , Youngrok Jang , Gyuyeol Kong , Sooyong Choi

This paper investigates reconfigurable intelligent surface (RIS)-aided frequency division duplexing (FDD) communication systems. Since the downlink and uplink signals are simultaneously transmitted in FDD, the phase shifts at the RIS should…

Information Theory · Computer Science 2024-01-23 Gyoseung Lee , Hyeongtaek Lee , Donghwan Kim , Jaehoon Chung , A. Lee. Swindlehurst , Junil Choi

Cell-free (CF) massive multiple-input multiple-output (MIMO) and reconfigurable intelligent surface (RIS) are two promising technologies for realizing future beyond-fifth generation (B5G) networks. In this paper, we consider a practical…

Information Theory · Computer Science 2023-06-16 Enyu Shi , Jiayi Zhang , Derrick Wing Kwan Ng , Bo Ai

Liquid crystal (LC) technology provides a low-power and scalable approach to implement a reconfigurable intelligent surface (RIS). However, the LC-based RIS's phase-shift response is inherently frequency-dependent, which can lead to…

Signal Processing · Electrical Eng. & Systems 2025-08-07 Mohamadreza Delbari , Qikai Zhou , Robin Neuder , Alejandro Jiménez-Sáez , Vahid Jamali

Reconfigurable intelligent surface (RIS) is regarded as a promising technology with great potential to boost wireless networks. Affected by the "double fading" effect, however, conventional passive RIS cannot bring considerable performance…

Signal Processing · Electrical Eng. & Systems 2022-10-06 Qi Zhu , Ming Li , Rang Liu , Yang Liu , Qian Liu

Reconfigurable intelligent surfaces (RISs) are widely considered to become an integral part of future wireless communication systems. Various methodologies exist to design such surfaces; however, most consider or require a very large number…

Optimization and Control · Mathematics 2023-09-01 Hans-Dieter Lang , Michel A. Nyffenegger , Heinz Mathis , Xingqi Zhang

The objective of this paper is to develop simple techniques to enhance the performance of multi-user RIS aided wireless systems. Specifically, we develop a novel technique called \textit{channel separation} which provides a better…

Information Theory · Computer Science 2022-09-14 Ikram Singh , Peter J. Smith , Pawel A. Dmochowski , Rua Murray

Reconfigurable Intelligent Surfaces (RISs) have emerged as a transformative technology for next-generation wireless communication systems, offering unprecedented control over electromagnetic wave propagation. In particular, Simultaneously…

Signal Processing · Electrical Eng. & Systems 2025-01-22 Rongguang Song , Haifan Yin , Xilong Pei , Lin Cao , Taorui Yang , Xue Ren , Yuanwei Liu

This paper considers the application of reconfigurable intelligent surfaces (RISs) (a.k.a. intelligent reflecting surfaces (IRSs)) to assist multiuser multiple-input multiple-output (MIMO) uplink transmission from several multi-antenna user…

Information Theory · Computer Science 2021-09-14 Li You , Jiayuan Xiong , Yufei Huang , Derrick Wing Kwan Ng , Cunhua Pan , Wenjin Wang , Xiqi Gao

We consider a practical spatially correlated reconfigurable intelligent surface (RIS)-aided cell-free (CF) massive multiple-input-multiple-output (mMIMO) system with multi-antenna access points (APs) over spatially correlated Rician fading…

Information Theory · Computer Science 2022-09-29 Enyu Shi , Jiayi Zhang , Zhe Wang , Derrick Wing Kwan Ng , Bo Ai

Reconfigurable intelligent surfaces (RISs) are envisioned to be a disruptive wireless communication technique that is capable of reconfiguring the wireless propagation environment. In this paper, we study a free-space RIS-assisted…

Information Theory · Computer Science 2022-09-19 Xin Cheng , Yan Lin , Weiping Shi , Jiayu Li , Cunhua Pan , Feng Shu , Yongpeng Wu , Jiangzhou Wang

The analysis and optimization of single intelligent reflecting surface (IRS)-assisted systems have been extensively studied, whereas little is known regarding multiple-IRS-assisted systems. This paper investigates the analysis and…

Information Theory · Computer Science 2022-06-07 Gengfa Ding , Feng Yang , Lianghui Ding , Ying Cui