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Reconfigurable intelligent surface (RIS) is a candidate technology for future wireless networks. It enables to shape the wireless environment to reach massive connectivity and enhanced data rate. The promising gains of RIS-assisted networks…

Signal Processing · Electrical Eng. & Systems 2022-06-09 Paulo R. B. Gomes , Gilderlan T. de Araújo , Bruno Sokal , André L. F. de Almeida , Behrooz Makki , Gábor Fodor

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 is a potential technology component of future wireless networks due to its capability of shaping the wireless environment. The promising MIMO systems in terms of extended coverage and enhanced capacity…

Information Theory · Computer Science 2022-07-07 Paulo R. B. Gomes , Gilderlan T. de Araújo , Bruno Sokal , André L. F. de Almeida , Behrooz Makki , Gábor Fodor

Intelligent reflecting surface (IRS) is an emerging technology for future wireless communications including 5G and especially 6G. It consists of a large 2D array of (semi-)passive scattering elements that control the electromagnetic…

Signal Processing · Electrical Eng. & Systems 2021-04-21 Gilderlan T. de Araújo , André L. F. de Almeida , Rémy Boyer

This letter proposes decision-directed semi-blind channel estimation for massive multiple-input multiple-output low-Earth-orbit satellite communications. Two semi-blind estimators are proposed. The first utilizes detected data symbols in…

Signal Processing · Electrical Eng. & Systems 2024-11-22 Abdollah Masoud Darya , Saeed Abdallah

A reconfigurable intelligent surface (RIS) reflects incoming signals in different ways depending on the phase-shift pattern assigned to its elements. The most promising use case is to aid the communication between a base station and a user…

Information Theory · Computer Science 2022-12-06 Emil Björnson , Parisa Ramezani

Reconfigurable intelligent surfaces (RISs) have been introduced as a remedy for mitigating frequent blockages in millimeter wave (mmWave) multiple-input multiple-output (MIMO) communication networks. However, perfect or nearly perfect…

Signal Processing · Electrical Eng. & Systems 2021-06-22 Rafaela Schroeder , Jiguang He , Markku Juntti

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

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

Beyond diagonal reconfigurable intelligent surface (BD-RIS), with its enhanced degrees of freedom compared to conventional RIS, has demonstrated notable potential for enhancing wireless communication performance. However, a key challenge in…

Signal Processing · Electrical Eng. & Systems 2025-09-15 Yijie Liu , Weidong Mei , He Sun , Dong Wang , Peilan Wang

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

In Reconfigurable intelligent surface (RIS)-assisted systems the acquisition of CSI and the optimization of the reflecting coefficients constitute a pair of salient design issues. In this paper, a novel channel training protocol is…

Information Theory · Computer Science 2021-06-01 Jiancheng An , Chao Xu , Li Wang , Yusha Liu , Lu Gan , Lajos Hanzo

Reconfigurable intelligent surfaces (RISs) have been recently considered as a promising candidate for energy-efficient solutions in future wireless networks. Their dynamic and lowpower configuration enables coverage extension, massive…

Information Theory · Computer Science 2022-07-05 Li Wei , Chongwen Huang , Qinghua Guo , Zhaohui Yang , Zhaoyang Zhang , George C. Alexandropoulos , Merouane Debbah , Chau Yuen

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

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

In this paper, we investigate the blind channel estimation problem for MIMO systems under Rayleigh fading channel. Conventional MIMO communication techniques require transmitting a considerable amount of training symbols as pilots in each…

Signal Processing · Electrical Eng. & Systems 2021-11-17 Jiancheng Tang , Qianqian Yang , Zhaoyang Zhang

This letter proposes a model for symbol detection in the uplink of IRS-assisted networks in the presence of channel aging. During the first stage, we model the received pilot signal as a tensor, which serves as a basis for both estimating…

Signal Processing · Electrical Eng. & Systems 2026-05-29 Kenneth B. A. Benicio , André L. F. de Almeida , Bruno Sokal , Fazal-E-Asim , Behrooz Makki , Gábor Fodor

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

To mitigate the effects of shadow fading and obstacle blocking, reconfigurable intelligent surface (RIS) has become a promising technology to improve the signal transmission quality of wireless communications by controlling the…

Information Theory · Computer Science 2021-11-10 Wangyang Xu , Jiancheng An , Yongjun Xu , Chongwen Huang , Lu Gan , Chau Yuen

This paper proposes a tensor-based parametric modeling and estimation framework in multiple-input multiple-output (MIMO) systems assisted by intelligent reflecting surfaces (IRSs). We present two algorithms that exploit the tensor structure…

Signal Processing · Electrical Eng. & Systems 2026-05-29 Kenneth B. A. Benício , André L. F. de Almeida , Bruno Sokal , Fazal-E-Asim , Behrooz Makki , Gabor Fodor