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Beyond diagonal reconfigurable intelligent surface (BD-RIS) refers to a family of RIS architectures characterized by scattering matrices not limited to being diagonal and enables higher wave manipulation flexibility and large performance…

Signal Processing · Electrical Eng. & Systems 2025-04-16 Rui Wang , Shuowen Zhang , Bruno Clerckx , Liang Liu

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

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

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

Reconfigurable intelligent surface (RIS) is very promising for wireless networks to achieve high energy efficiency, extended coverage, improved capacity, massive connectivity, etc. To unleash the full potentials of RIS-aided communications,…

Information Theory · Computer Science 2022-01-03 Yabo Guo , Peng Sun , Zhengdao Yuan , Chongwen Huang , Qinghua Guo , Zhongyong Wang , Chau Yuen

Extremely large-scale massive MIMO (XL-MIMO) is a promising technique for future 6G communications.However, existing far-field or near-field channel model mismatches the hybrid-field channel feature in the practical XL-MIMO…

Information Theory · Computer Science 2021-11-23 Xiuhong Wei , Linglong Dai

In this paper, we study the high-resolution channel estimation problem for intelligent reflecting surface (IRS)-assisted millimeter wave (mmWave) multiple-input-multiple-output (MIMO) communications, which is a prerequisite to guarantee…

Signal Processing · Electrical Eng. & Systems 2020-06-23 C. Jia , J. Cheng , H. Gao , W. Xu

Accurate channel estimation is essential for reliable communication in sub-THz extremely large (XL) MIMO systems. Deploying XL-MIMO in high-frequency bands not only increases the number of antennas, but also fundamentally alters channel…

Signal Processing · Electrical Eng. & Systems 2025-04-15 Wen-Xuan Long , Marco Moretti , Michele Morelli , Luca Sanguinetti , Rui Chen

Double-reconfigurable intelligent surface (RIS) is a promising technique, achieving a substantial gain improvement compared to single-RIS techniques. However, in double-RIS-aided systems, accurate channel estimation is more challenging than…

Information Theory · Computer Science 2022-11-30 Songjie Yang , Wanting Lyu , Yue Xiu , Zhongpei Zhang , Chau Yuen

This paper investigates the uplink cascaded channel estimation for intelligent-reflecting-surface (IRS)-assisted multi-user multiple-input-single-output systems. We focus on a sub-6 GHz scenario where the channel propagation is not sparse…

Signal Processing · Electrical Eng. & Systems 2022-09-07 Huayan Guo , Vincent K. N. Lau

A reconfigurable intelligent surface (RIS) can shape the radio propagation environment by virtue of changing the impinging electromagnetic waves towards any desired directions, thus, breaking the general Snell's reflection law. However, the…

Signal Processing · Electrical Eng. & Systems 2021-01-15 Jiguang He , Henk Wymeersch , Markku Juntti

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

Near-field communication comes to be an indispensable part of the future sixth generation (6G) communications at the arrival of the forth-coming deployment of extremely large-scale multiple-input-multiple-output (XL-MIMO) systems. Due to…

Signal Processing · Electrical Eng. & Systems 2024-09-04 Haochen Wu , Liyang Lu , Zhaocheng Wang

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 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

A reconfigurable intelligent surface (RIS) can shape the radio propagation by passively changing the directions of impinging electromagnetic waves. The optimal control of the RIS requires perfect channel state information (CSI) of all the…

Signal Processing · Electrical Eng. & Systems 2020-02-18 Jiguang He , Markus Leinonen , Henk Wymeersch , Markku Juntti

To achieve the more promising passive beamforming gains in the double-intelligent reflecting surface (IRS) assisted system over the conventional single-IRS system, channel estimation is practically indispensable but also a more challenging…

Information Theory · Computer Science 2020-10-14 Beixiong Zheng , Changsheng You , Rui Zhang

To achieve the more significant passive beamforming gain in the double-intelligent reflecting surface (IRS) aided system over the conventional single-IRS counterpart, channel state information (CSI) is indispensable in practice but also…

Information Theory · Computer Science 2021-03-12 Beixiong Zheng , Changsheng You , Rui Zhang

Extremely large reconfigurable intelligent surface (XL-RIS) is emerging as a promising key technology for 6G systems. To exploit XL-RIS's full potential, accurate channel estimation is essential. This paper investigates channel estimation…

Signal Processing · Electrical Eng. & Systems 2024-09-26 Peicong Zheng , Xuantao Lyu , Ye Wang , Yi Gong

Accurate channel model and channel estimation are essential to empower extremely large-scale MIMO (XL-MIMO) in 6G networks with ultra-high spectral efficiency. With the sharp increase in the antenna array aperture of the XL-MIMO scenario,…

Information Theory · Computer Science 2023-04-25 Yu Lu , Linglong Dai