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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

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) is a promising technology to enhance the spectral and energy efficiency in a wireless communication system. The design of the phase shifts of an RIS in every channel coherence interval demands a huge…

Signal Processing · Electrical Eng. & Systems 2024-05-15 Sadaf Syed , Dominik Semmler , Donia Ben Amor , Michael Joham , Wolfgang Utschick

We consider a scalable user-centric cell-free massive MIMO network with distributed remote radio units (RUs), enabling macrodiversity and joint processing. Due to the limited uplink (UL) pilot dimension, multiuser interference in the UL…

Information Theory · Computer Science 2022-06-09 Fabian Göttsch , Noboru Osawa , Takeo Ohseki , Kosuke Yamazaki , Giuseppe Caire

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

Reconfigurable intelligent surfaces (RISs) have emerged as a promising technology to enhance the performance of sixth-generation (6G) and beyond communication systems. The passive nature of RISs and their large number of reflecting elements…

Information Theory · Computer Science 2024-06-12 Nipuni Ginige , Arthur Sousa de Sena , Nurul Huda Mahmood , Nandana Rajatheva , Matti Latva-aho

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

Near-field communications present new opportunities over near-field channels, however, the spherical wavefront propagation makes near-field signal processing challenging. In this context, this paper proposes efficient near-field channel…

Information Theory · Computer Science 2023-04-04 Songjie Yang , Chenfei Xie , Wanting Lyu , Boyu Ning , Zhongpei Zhang , Chau Yuen

Reconfigurable intelligent surfaces (RIS) are passive controllable arrays of small reflectors that direct electromagnetic energy towards or away from the target nodes, thereby allowing better management of signals and interference in a…

Information Theory · Computer Science 2023-01-13 Bharath Shamasundar , Negar Daryanavardan , Aria Nosratinia

Orthogonal multi-user multiple-input multiple-output (MU-MIMO) channels allow for optimum performance with simplified precoding/equalization, and they achieve maximum multiplexing gain which is shared fairly among users. Reconfigurable…

Information Theory · Computer Science 2023-05-01 Juan Vidal Alegria , Fredrik Rusek

Large beam training overhead has been considered as one of main issues in the channel estimation for reconfigurable intelligent surface (RIS)-aided systems. In this paper, we propose an atomic norm minimization (ANM)-based low-overhead…

Signal Processing · Electrical Eng. & Systems 2021-07-21 Hyeonjin Chung , Sunwoo Kim

We address the problem of fast time-varying channel estimation in millimeter-wave (mmWave) MIMO systems with imperfect channel state information (CSI) and facilitate efficient channel reconstruction. Specifically, leveraging the low-rank…

Signal Processing · Electrical Eng. & Systems 2025-11-11 Tianyu Jiang , Yan Yang , Hongjin Liu , Runyu Han , Bo Ai , Mohsen Guizani

Millimeter wave (mmWave) communications and reconfigurable intelligent surfaces (RIS) are two critical technologies for next-generation networks, especially in dense indoor environments. However, existing analyses often oversimplify the…

Systems and Control · Electrical Eng. & Systems 2025-10-15 Zhi Chai , Jiajie Xu , Justin P. Coon , Mohamed-Slim Alouini

Reconfigurable intelligent surface (RIS) is a promising technology for future wireless communications due to its capability of optimizing the propagation environments. Nevertheless, in literature, there are few prototypes serving multiple…

Signal Processing · Electrical Eng. & Systems 2024-05-14 Zhibo Zhou , Haifan Yin , Li Tan , Ruikun Zhang , Kai Wang , Yingzhuang Liu

We propose a channel estimation protocol to determine the uplink channel state information (CSI) at the base station for an intelligent reflecting surface (IRS) based wireless communication. More specifically, we develop a channel…

Signal Processing · Electrical Eng. & Systems 2025-04-15 Swapnil Saha , Md. Forkan Uddin

With the growing number of users in multi-user multiple-input multiple-output (MU-MIMO) systems, demodulation reference signals (DMRSs) are efficiently multiplexed in the code domain via orthogonal cover codes (OCC) to ensure orthogonality…

Signal Processing · Electrical Eng. & Systems 2025-06-16 Jiawei Zhuang , Hongwei Hou , Minjie Tang , Wenjin Wang , Shi Jin , Vincent K. N. Lau

We consider a narrowband MIMO reconfigurable intelligent surface (RIS)-assisted wireless communication system and use tensor signal modelling techniques to individually estimate all communication channels including the non-RIS channels…

Signal Processing · Electrical Eng. & Systems 2023-11-03 Alexander James Fernandes , Ioannis Psaromiligkos

In a multi-user millimeter (mm) wave communication system, we consider the problem of estimating the channel response between the central node (base station) and each of the user equipments (UE). We propose three different strategies: 1)…

Information Theory · Computer Science 2017-03-17 Manoj A , Arun Pachai Kannu

Reconfigurable intelligent surface (RIS)-assisted terahertz (THz) communication is emerging as a key technology to support ultra-high data rates in future sixth-generation networks. However, the acquisition of accurate channel state…

Information Theory · Computer Science 2025-06-17 Xin Su , Ruisi He , Peng Zhang , Bo Ai , Yong Niu , Gongpu Wang

Reconfigurable intelligent surfaces (RISs) are one of the foremost technological enablers of future wireless systems. They improve communication and localization by providing a strong non-line-of-sight path to the receiver. In this paper,…

Signal Processing · Electrical Eng. & Systems 2022-04-26 Kamran Keykhosravi , Henk Wymeersch