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This paper proposes a novel reconfigurable intelligent surface (RIS) architecture which enables channel estimation of RIS-assisted millimeter wave (mmWave) systems. More specifically, two channel estimation methods, namely, direct…

Information Theory · Computer Science 2020-08-20 Fangqing Jiang , Liang Yang , Daniel Benevides da Costa , Qingqing Wu

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

Intelligent reflecting surfaces (IRSs) improve both the bandwidth and energy efficiency of wideband communication systems by using low-cost passive elements for reflecting the impinging signals with adjustable phase shifts. To realize the…

Signal Processing · Electrical Eng. & Systems 2021-06-08 Siqi Ma , Wenqian Shen , Jianping An , Lajos Hanzo

Reconfigurable intelligent surfaces (RISs) have attracted great attention as a potential beyond 5G technology. These surfaces consist of many passive elements of metamaterials whose impedance can be controllable to change the phase,…

Information Theory · Computer Science 2021-09-09 Özlem Tuğfe Demir , Emil Björnson

The use of multiple Reconfigurable Intelligent Sur- faces (RIS) has gained attention in 6G networks to enhance coverage. However, the feasibility of deploying multiple RIS relies on efficient channel estimation and reduced pilot overhead.…

Information Theory · Computer Science 2025-11-25 Roberto C. G. Porto , Rodrigo C. de Lamare

Emerging technologies, such as holographic multiple-input multiple-output (HMIMO) and stacked intelligent metasurface (SIM), are driving the development of wireless communication systems. Specifically, the SIM is physically constructed by…

Information Theory · Computer Science 2024-03-12 Xianghao Yao , Jiancheng An , Lu Gan , Marco Di Renzo , Chau Yuen

To achieve the joint active and passive beamforming gains in the reconfigurable intelligent surface assisted millimeter wave system, the reflected cascade channel needs to be accurately estimated. Many strategies have been proposed in the…

Information Theory · Computer Science 2021-09-22 Yiming Liu , Erwu Liu , Rui Wang , Zhu Han , Binyu Lu

Millimeter (mm) wave massive MIMO has the potential for delivering orders of magnitude increases in mobile data rates, with compact antenna arrays providing narrow steerable beams for unprecedented levels of spatial reuse. A fundamental…

Signal Processing · Electrical Eng. & Systems 2018-12-05 Maryam Eslami Rasekh , Upamanyu Madhow

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

Reconfigurable intelligent surface (RIS)-aided terahertz (THz)-band communications are promising enablers for future wireless networks. However, array densification at high frequencies introduces significant challenges in accurate channel…

Signal Processing · Electrical Eng. & Systems 2025-05-16 Ahmad Dkhan , Simon Tarboush , Hadi Sarieddeen , Ibrahim Abou-Faycal , Tareq Y. Al-Naffouri

Channel estimation is the main hurdle to reaping the benefits promised by the intelligent reflecting surface (IRS), due to its absence of ability to transmit/receive pilot signals as well as the huge number of channel coefficients…

Signal Processing · Electrical Eng. & Systems 2021-06-23 Rui Wang , Liang Liu , Shuowen Zhang , Changyuan Yu

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 surface (RIS) constitutes an essential and promising paradigm that relies programmable wireless environment and provides capability for space-intensive communications, due to the use of low-cost massive reflecting…

Information Theory · Computer Science 2021-12-10 Yu Jin , Jiayi Zhang , Chongwen Huang , Liang Yang , Huahua Xiao , Bo Ai , Zhiqin Wang

In intelligent reflecting surface (IRS) assisted communication systems, the acquisition of channel state information (CSI) is a crucial impediment for achieving the beamforming gain of IRS because of the considerable overhead required for…

Information Theory · Computer Science 2020-06-25 Zhaorui Wang , Liang Liu , Shuguang Cui

Existing works mainly rely on the far-field planar-wave-based channel model to assess the performance of reconfigurable intelligent surface (RIS)-enabled wireless communication systems. However, when the transmitter and receiver are in…

Signal Processing · Electrical Eng. & Systems 2024-03-20 Hao Jiang , Wangqi Shi , Zaichen Zhang , Cunhua Pan , Qingqing Wu , Feng Shu , Ruiqi Liu , Jiangzhou Wang

The rapid development of 6G systems demands advanced technologies to boost network capacity and spectral efficiency, particularly in the context of intelligent reflecting surfaces (IRS)-aided millimeter-wave (mmWave) communications. A key…

Signal Processing · Electrical Eng. & Systems 2026-01-19 Xiaokun Tuo , Zijian Chen , Ming-Min Zhao , Changsheng You , Min-Jian Zhao

Amid the demand for densely integrated elements in techniques such as holographic reconfigurable intelligent surfaces (RISs), the mutual coupling effect has gained prominence. By performing a misspecified Cramer-Rao bound analysis within an…

Signal Processing · Electrical Eng. & Systems 2024-02-21 Pinjun Zheng , Xiuxiu Ma , Tareq Y. Al-Naffouri

This paper proposes tensor-based channel estimation for reconfigurable intelligent surface (RIS)-assisted communication networks. We exploit the inherent geometrical structure of the Terahertz propagation channel, including the antenna…

Signal Processing · Electrical Eng. & Systems 2024-11-06 Fazal-E-Asim , Bruno Sokal , André L. F. de Almeida , Behrooz Makki , Gábor Fodor

Reconfigurable intelligent surfaces (RISs) have attracted increasing interest from both academia and industry, thanks to their unique features on controlling electromagnetic (EM) waves. Although theoretical models for RIS-empowered…

Information Theory · Computer Science 2024-03-05 Jian Sang , Jifeng Lan , Mingyong Zhou , Boning Gao , Wankai Tang , Xiao Li , Michail Matthaiou , Shi Jin , Marco Di Renzo

Hybrid analog and digital precoding allows millimeter wave (mmWave) systems to achieve both array and multiplexing gain. The design of the hybrid precoders and combiners, though, is usually based on knowledge of the channel. Prior work on…

Information Theory · Computer Science 2016-11-15 Kiran Venugopal , Ahmed Alkhateeb , Nuria González Prelcic , Robert W. Heath