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Reconfigurable Intelligent Surfaces (RISs) have been recently considered as an energy-efficient solution for future wireless networks due to their fast and low-power configuration, which has increased potential in enabling massive…

Information Theory · Computer Science 2022-06-27 Li Wei , Chongwen Huang , George C. Alexandropoulos , Chau Yuen , Zhaoyang Zhang , Mérouane Debbah

Reconfigurable Intelligent Surface (RIS) technology has emerged as a key enabler for future wireless communications. However, its potential is constrained by the difficulty of acquiring accurate user-to-RIS channel state information (CSI),…

Signal Processing · Electrical Eng. & Systems 2026-04-20 Md. Shahriar Sadid , Ali A. Nasir , Saad Al-Ahmadi , Samir Al-Ghadhban

A significant increase in the number of reconfigurable intelligent surface (RIS) elements results in a spherical wavefront in the near field of extremely large-scale RIS (XL-RIS). Although the channel matrix of the cascaded two-hop link may…

Signal Processing · Electrical Eng. & Systems 2023-11-14 Zixing Tang , Yuanbin Chen , Ying Wang , Tianqi Mao , Qingqing Wu , Marco Di Renzo , Lajos Hanzo

This paper proposes a correlation-based three-stage channel estimation strategy with low pilot overhead for reconfigurable intelligent surface (RIS)-aided millimeter wave (mmWave) multi-user (MU) MIMO systems, in which both users and base…

Signal Processing · Electrical Eng. & Systems 2025-02-11 Liuchang Zhuo , Cunhua Pan , Hong Ren , Ruisong Weng , Shi Jin , A. Lee Swindlehurst , Jiangzhou Wang

Reconfigurable intelligent surfaces (RISs) have been proposed as a key enabler to improve the coverage of the signals and mitigate the frequent blockages in millimeter wave (mmWave) multiple-input multiple-output (MIMO) communications.…

Signal Processing · Electrical Eng. & Systems 2021-07-16 Rafaela Schroeder , Jiguang He , Glauber Brante , Markku Juntti

We consider the data-aided channel estimation (CE) problem in a reconfigurable intelligent surface (RIS)-assisted wireless communication system, where the channel and information symbols are estimated jointly during the CE phase,…

Signal Processing · Electrical Eng. & Systems 2025-06-17 Amarilton Lopes Magalhães , André Lima Férrer de Almeida , Gilderlan Tavares de Araújo

In the realm of reconfigurable intelligent surface (RIS)-assisted communication systems, the connection between a base station (BS) and user equipment (UE) is formed by a cascaded channel, merging the BS-RIS and RIS-UE channels. Due to the…

Signal Processing · Electrical Eng. & Systems 2024-09-13 Yiming Cui , Jiajia Guo , Chao-Kai Wen , Shi Jin

Accurate estimation of the cascaded channel from a user equipment (UE) to a base station (BS) via each reconfigurable intelligent surface (RIS) element is critical to realizing the full potential of the RIS's ability to control the overall…

Signal Processing · Electrical Eng. & Systems 2024-11-08 Özlem Tuğfe Demir , Emil Björnson , Luca Sanguinetti

Channel estimation in reconfigurable intelligent surfaces (RIS)-aided systems is crucial for optimal configuration of the RIS and various downstream tasks such as user localization. In RIS-aided systems, channel estimation involves…

Signal Processing · Electrical Eng. & Systems 2023-12-19 Firas Fredj , Amal Feriani , Amine Mezghani , Ekram Hossain

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

To reap the benefits of reconfigurable intelligent surfaces (RIS), channel state information (CSI) is generally required. However, CSI acquisition in RIS systems is challenging and often results in very large pilot overhead, especially in…

Signal Processing · Electrical Eng. & Systems 2023-09-21 Ly V. Nguyen , A. Lee Swindlehurst

Channel estimation is challenging for the reconfigurable intelligence surface (RIS) assisted millimeter wave (mmWave) communications. Since the number of coefficients of the cascaded channels in such systems is closely dependent on the…

Signal Processing · Electrical Eng. & Systems 2021-06-22 Yushan Liu , Shun Zhang , Feifei Gao , Jie Tang , Octavia A. Dobre

Reconfigurable intelligent surface (RIS) is considered as a revolutionary technology for future wireless communication networks. In this letter, we consider the acquisition of the time-varying cascaded channels, which is a challenging task…

Signal Processing · Electrical Eng. & Systems 2021-08-13 Meng Xu , Shun Zhang , Jianpeng Ma , Octavia A. Dobre

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

In this paper, we propose a novel two-stage based uplink channel estimation strategy with reduced pilot overhead and error propagation for a reconfigurable intelligent surface (RIS)-aided multi-user (MU) millimeter wave (mmWave) system.…

Signal Processing · Electrical Eng. & Systems 2022-08-24 Zhendong Peng , Cunhua Pan , Gui Zhou , Hong Ren

Non-diagonal reconfigurable intelligent surfaces (RISs) offer enhanced wireless signal manipulation over conventional RIS by enabling the incident signal on any of its $M$ elements to be reflected from another element via an $M \times M$…

Signal Processing · Electrical Eng. & Systems 2025-06-19 Mostafa Samy , Hayder Al-Hraishawi , Abuzar B. M. Adam , Madyan Alsenwi , Symeon Chatzinotas , Björn Otteresten

In reconfigurable intelligent surface (RIS)-assisted millimeter-wave (mmWave) communication systems, the large-scale RIS introduces pronounced geometric effects that lead to the coexistence of far-field and near-field propagation.…

Signal Processing · Electrical Eng. & Systems 2026-02-09 Xiaokun Tuo , Ming-Min Zhao , Xiang Wang , Changsheng You , Min-Jian Zhao

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

Reconfigurable Intelligent Surface (RIS) is considered as an energy-efficient solution for future wireless communication networks due to its fast and low-cost configuration. In this letter, we consider the estimation of cascaded channels in…

Signal Processing · Electrical Eng. & Systems 2022-10-25 Mengbing Liu , Xin Li , Boyu Ning , Chongwen Huang , Sumei Sun , Chau Yuen

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