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This paper investigates the two-timescale transmission design for reconfigurable intelligent surface (RIS)-aided massive multiple-input multiple-output (MIMO) systems, where the beamforming at the base station (BS) is adapted to the…

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

Reconfigurable intelligent surface (RIS) is an attractive technology to improve the transmission rate of millimetre-wave (mmWave) communication systems. The previous {research} on RIS technology mainly focused on improving the transmission…

Signal Processing · Electrical Eng. & Systems 2022-11-01 Yunis Xanthos , Wanting Lyu , Songjie Yang , Chadi Assi , Xianbing Zou , Ning Wei

This paper studies RIS-aided cell-free massive MIMO systems, where multiple RISs are deployed to assist the communication between multiple access points (APs) and multiple users, with either continuous or discrete phase shifts at the RISs.…

Information Theory · Computer Science 2021-12-14 Si-Nian Jin , Dian-Wu Yue , Ha H. Nguyen

Reconfigurable intelligent surfaces (RISs), which enable tunable anomalous reflection, have appeared as a promising method to enhance wireless systems. In this paper, we propose to use an RIS as a spatial equalizer to address the well-known…

Information Theory · Computer Science 2021-03-10 Hongliang Zhang , Lingyang Song , Zhu Han , H. Vincent Poor

The objective of this paper is to evaluate the effectiveness of a two-timescale transmission design in cell-free massive multi-input multiple-output (MIMO) systems incorporating reconfigurable intelligent surfaces (RISs) under the…

Signal Processing · Electrical Eng. & Systems 2023-04-06 Mahdi Eskandari , Kangda Zhi , Huiling Zhu , Cunhua Pan , Jiangzhou Wang

Reconfigurable intelligent surface (RIS) is a promising reflective radio technology for improving the coverage and rate of future wireless systems by reconfiguring the wireless propagation environment. The current work mainly focuses on the…

Networking and Internet Architecture · Computer Science 2021-03-24 Xuelin Cao , Bo Yang , Hongliang Zhang , Chongwen Huang , Chau Yuen , Zhu Han

The fluid antenna (FA) index modulation (IM)-enabled multiple-input multiple-output (MIMO) system, referred to as FA-IM, significantly enhances spectral efficiency (SE) compared to the conventional FA-assisted MIMO system. To improve…

Information Theory · Computer Science 2024-12-31 Xinghao Guo , Yin Xu , Dazhi He , Cixiao Zhang , Hanjiang Hong , Kai-Kit Wong , Wenjun Zhang , Yiyan Wu

As the dense deployment of access points (APs) in cell-free massive multiple-input multiple-output (CF-mMIMO) systems presents significant challenges, per-AP coverage can be expanded using large-scale antenna arrays (LAAs). However, this…

Signal Processing · Electrical Eng. & Systems 2025-10-17 Eunhyuk Park , Seok-Hwan Park , Osvaldo Simeone , Marco Di Renzo , Shlomo Shamai

Intelligent surfaces that reshape electromagnetic waves are regarded as disruptive technologies for wireless networks. However, existing designs sit at two costly extremes: dynamic reconfigurable intelligent surfaces (RISs) offer fine beam…

Signal Processing · Electrical Eng. & Systems 2025-11-24 Ziyuan Zheng , Qingqing Wu , Wen Chen , Weiren Zhu , Ying Gao

As an emerging wireless communication technology, reconfigurable intelligent surface (RIS) has become a basic choice for providing signal coverage services in scenarios with dense obstacles or long tunnels through multi-hop configurations.…

Information Theory · Computer Science 2024-07-16 Rujing Xiong , Jialong Lu , Jianan Zhang , Minggang Liu , Xuehui Dong , Tiebin Mi , Robert Caiming Qiu

Movable antennas (MAs) are a promising technology to achieve a significant enhancement in rate for future wireless networks. The pioneering investigation on near-field directional modulation design for a reconfigurable intelligent surface…

Signal Processing · Electrical Eng. & Systems 2025-06-03 Maolin Li , Feng Shu , Riqing Chen , Cunhua Pan , Yongpeng Wu

Reconfigurable intelligent surfaces (RIS)-assisted massive multiple-input multiple-output (mMIMO) is a promising technology for applications in next-generation networks. However, reflecting-only RIS provides limited coverage compared to a…

Information Theory · Computer Science 2023-09-18 Anastasios Papazafeiropoulos , Le-Nam Tran , Zaid Abdullah , Pandelis Kourtessis , Symeon Chatzinotas

In this paper, we propose a transmission mechanism for a reconfigurable intelligent surface (RIS)-assisted millimeter wave (mmWave) system based on cluster index modulation (CIM), named best-gain optimized cluster selection CIM (BGCS-CIM).…

Signal Processing · Electrical Eng. & Systems 2023-07-11 Mahmoud Raeisi , Asil Koc , Ibrahim Yildirim , Ertugrul Basar , Tho Le-Ngoc

Spatial multiplexing (SMX) multiple-input multiple-output (MIMO) over the best beamspace was considered as the best solution for millimeter wave (mmWave) communications regarding spectral efficiency (SE), referred as the best beamspace…

Signal Processing · Electrical Eng. & Systems 2018-10-26 Shuaishuai Guo , Haixia Zhang , Peng Zhang , Pengjie Zhao , Leiyu Wang , Mohamed-Slim Alouini

Reconfigurable Intelligent Surfaces (RIS) represent a transformative technology for sixth-generation (6G) wireless communications, but it suffers from a significant limitation, namely the double-fading attenuation. Active RIS has emerged as…

Information Theory · Computer Science 2025-04-23 Yang Cao , Wenchi Cheng , Jingqing Wang , Wei Zhang

The incorporation of reconfigurable intelligent surface (RIS) into massive multiple-input-multiple-output (mMIMO) systems can unleash the potential of next-generation networks by improving the performance of user equipments (UEs) in service…

Information Theory · Computer Science 2022-09-12 Anastasios Papazafeiropoulos , Ioannis Krikidis , Pandelis Kourtessis

Reconfigurable intelligent surface (RIS) is a novel meta-material which can form a smart radio environment by dynamically altering reflection directions of the impinging electromagnetic waves. In the prior literature, the inter-RIS links…

Information Theory · Computer Science 2024-03-13 Kaizhe Xu , Jiajia Guo , Jun Zhang , Shi Jin , Shaodan Ma

Reconfigurable Intelligent Surfaces (RISs) are announced as a truly transformative technology, capable of smartly shaping wireless environments to optimize next-generation communication networks. Among their numerous foreseen applications,…

Signal Processing · Electrical Eng. & Systems 2023-06-21 Moustafa Rahal , Benoit Denis , Taghrid Mazloum , Frederic Munoz , Raffaele D Errico

We consider a practical spatially correlated reconfigurable intelligent surface (RIS)-aided cell-free (CF) massive multiple-input-multiple-output (mMIMO) system with multi-antenna access points (APs) over spatially correlated Rician fading…

Information Theory · Computer Science 2022-09-29 Enyu Shi , Jiayi Zhang , Zhe Wang , Derrick Wing Kwan Ng , Bo Ai