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The reconfigurable intelligent surface (RIS) plays an important role in maintaining the connectivity in millimeter wave (mmWave) MIMO systems when the direct channel between the transceivers is blocked. However, it is difficult to acquire…

Signal Processing · Electrical Eng. & Systems 2021-03-04 Rafaela Schroeder , Jiguang He , Markku Juntti

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

Reconfigurable intelligent surface (RIS) can manipulate the wireless communication environment by controlling the coefficients of RIS elements. However, due to the large number of passive RIS elements without signal processing capability,…

Information Theory · Computer Science 2021-01-26 Xiuhong Wei , Decai Shen , Linglong Dai

Channel estimation is challenging for the reconfigurable intelligent surface (RIS)-aided wireless communications. Since the number of coefficients of the cascaded channel among the base station (BS), the RIS and the user equipments (UEs) is…

Signal Processing · Electrical Eng. & Systems 2020-05-19 Chen Hu , Linglong Dai

Reconfigurable intelligent surface (RIS) is envisioned to be a promising green technology to reduce the energy consumption and improve the coverage and spectral efficiency of massive multiple-input multiple-output (MIMO) wireless networks.…

Information Theory · Computer Science 2021-02-12 Zhen-Qing He , Hang Liu , Xiaojun Yuan , Ying-Jun Angela Zhang , Ying-Chang Liang

In this paper, we investigate the channel estimation challenge in reconfigurable intelligent surface (RIS)-aided near-field communication systems. Current channel estimation techniques require substantial pilot overhead and computational…

Signal Processing · Electrical Eng. & Systems 2025-04-29 Jeongjae Lee , Songnam Hong

Reconfigurable intelligent surface (RIS) has received widespread attention owing to the superiority of changing the wireless propagation environment intelligently. Channel feedback is essential in frequency division duplex (FDD)…

Information Theory · Computer Science 2020-12-08 Decai Shen , Linglong Dai

Reconfigurable intelligent surface (RIS) has been explored as a supportive technology for wireless communication since around 2019. While the literature highlights the potential of RIS in different modern applications, two key issues have…

Signal Processing · Electrical Eng. & Systems 2025-06-10 Daniel C. Alcantara , Daniel V. C. de Oliveira , Gilderlan T. de Araújo , Paulo R. B. Gomes , André L. F. de Almeida

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

The deployment of multiple reconfigurable intelligent surfaces (RISs) enhances the propagation environment by improving channel quality, but it also complicates channel estimation. Following the conventional wireless communication system…

Information Theory · Computer Science 2024-11-22 Weicong Chen , Yu Han , Chao-Kai Wen , Xiao Li , Shi Jin

Reconfigurable intelligent surfaces (RISs) have tremendous potential to boost communication performance, especially when the line-of-sight (LOS) path between the user equipment (UE) and base station (BS) is blocked. To control the RIS,…

Signal Processing · Electrical Eng. & Systems 2023-11-21 Fan Jiang , Andrea Abrardo , Kamran Keykhoshravi , Henk Wymeersch , Davide Dardari , Marco Di Renzo

Reconfigurable Intelligent Surfaces (RISs) are envisioned to play a key role in future wireless communications, enabling programmable radio propagation environments. They are usually considered as almost passive planar structures that…

Information Theory · Computer Science 2022-08-12 Haiyang Zhang , Nir Shlezinger , George C Alexandropoulos , Idban Alamzadeh , Mohammadreza F Imani , Yonina C Eldar

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 surface (RIS) is considered a prospective technology for beyond fifth-generation (5G) networks to improve the spectral and energy efficiency at a low cost. Prior works on the RIS mainly rely on perfect channel…

Signal Processing · Electrical Eng. & Systems 2023-09-11 Sadaf Syed , Dominik Semmler , Donia Ben Amor , Michael Joham , Wolfgang Utschick

The channel estimation (CE) overhead for unstructured multipath-rich channels increases linearly with the number of reflective elements of reconfigurable intelligent surface (RIS). This results in a significant portion of the channel…

Networking and Internet Architecture · Computer Science 2024-09-02 Souvik Deb , Sasthi C. Ghosh

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

Reconfigurable intelligent surface (RIS) is envisioned to be an essential component of the paradigm for beyond 5G networks as it can potentially provide similar or higher array gains with much lower hardware cost and energy consumption…

Information Theory · Computer Science 2020-07-09 Hang Liu , Xiaojun Yuan , Ying-Jun Angela Zhang

Reconfigurable intelligent surfaces (RISs) have emerged as a promising solution that can provide dynamic control over the propagation of electromagnetic waves. The RIS technology is envisioned as a key enabler of sixth-generation networks…

Signal Processing · Electrical Eng. & Systems 2025-02-26 Ishan Koralege , Arthur S. de Sena , Nurul H. Mahmood , Farjam Karim , Dimuthu Lesthuruge , Samitha Gunarathne

The channel estimation overhead of reconfigurable intelligent surface (RIS) assisted communication systems can be prohibitive. Prior works have demonstrated via simulations that grouping neighbouring RIS elements can help to reduce the…

Information Theory · Computer Science 2021-11-23 Neel Kanth Kundu , Zan Li , Junhui Rao , Shanpu Shen , Matthew R. McKay , Ross Murch

In reconfigurable intelligent surface (RIS)-assisted systems, the optimization of the phase shifts requires separate acquisition of the channel state information (CSI) for the direct and RIS-assisted channels, posing significant design…

Information Theory · Computer Science 2022-03-30 Kevin Weinberger , Aydin Sezgin