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Extremely large-scale multiple-input multiple-output (XL-MIMO) is a key enabling technology for sixth-generation (6G) communication systems. Nevertheless, the increase in array aperture and signal bandwidth brings new challenges to wideband…

Signal Processing · Electrical Eng. & Systems 2026-04-23 Qingxia Feng , Yin Fang , Meng Hua , Cheng Zhang , Chunguo Li , Yongming Huang , Luxi Yang

We consider the problem of channel estimation in a multiple-input-multiple-output (MIMO) full-duplex (FD) wireless communication system assisted by a reconfigurable intelligent surface (RIS) with hardware impairments (HI) occurring at the…

Signal Processing · Electrical Eng. & Systems 2023-07-25 Alexander James Fernandes , Ioannis Psaromiligkos

In strong line-of-sight millimeter-wave (mmWave) wireless systems, the rank-deficient channel severely hampers spatial multiplexing. To address this inherent deficiency, multiple reconfigurable-intelligent-surfaces (RISs) are introduced in…

Information Theory · Computer Science 2023-05-05 Weicong Chen , Chao-Kai Wen , Xiao Li , Shi Jin

A reconfigurable intelligent surface (RIS) can be used to improve the channel gain between a base station (BS) and user equipment (UE), but only if its $N$ reflecting elements are configured properly. This requires accurate estimation of…

Signal Processing · Electrical Eng. & Systems 2022-05-24 Özlem Tuğfe Demir , Emil Björnson , Luca Sanguinetti

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

A fundamental challenge in millimeter-wave (mmWave) communication is the susceptibility to blocking objects. One way to alleviate this problem is the use of reconfigurable intelligent surfaces (RIS). Nevertheless, due to the large number of…

Information Theory · Computer Science 2022-04-22 Yaoshen Cui , Haifan Yin , Li Tan , Marco Di Renzo

In this paper, we investigate multi-user modular extremely large-scale multiple-input multiple-output (XL-MIMO) communication systems, where modular extremely large-scale uniform linear array (XL-ULA) is deployed at the base station (BS) to…

Information Theory · Computer Science 2023-08-24 Xinrui Li , Zhenjun Dong , Yong Zeng , Shi Jin , Rui Zhang

Reconfigurable Intelligent Surfaces (RISs) are envisioned to play a key role in future wireless communications, enabling programmable radio propagation environments. They are usually considered as nearly passive planar structures that…

Signal Processing · Electrical Eng. & Systems 2022-02-14 Haiyang Zhang , Nir Shlezinger , Idban Alamzadeh , George C. Alexandropoulos , Mohammadreza F. Imani , Yonina C. Eldar

In this paper, we utilize tools from stochastic geometry to estimate the interference propagation via reconfigurable intelligent surface (RIS) in the millimeter wave (mmWave, 30-300 GHz) band and specifically on the D band (110-170 GHz).…

Information Theory · Computer Science 2021-07-15 Joonas Kokkoniemi , Markku Juntti

The upper mid-band (UMB) spectrum is a key enabler for 6G systems, yet reconfigurable intelligent surface (RIS)-assisted UMB communications face severe channel estimation challenges due to near-field propagation and transitional scattering,…

Signal Processing · Electrical Eng. & Systems 2026-03-09 Jeongjae Lee , Chanwon Kim , Songnam Hong

Reconfigurable intelligent surfaces (RISs) represent a new technology that can shape the radio wave propagation and thus offers a great variety of possible performance and implementation gains. Motivated by this, we investigate the…

Information Theory · Computer Science 2023-02-08 Nemanja Stefan Perović , Le-Nam Tran , Marco Di Renzo , Mark F. Flanagan

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

The accurate estimation of Channel State Information (CSI) is of crucial importance for the successful operation of Multiple-Input Multiple-Output (MIMO) communication systems, especially in a Multi-User (MU) time-varying environment and…

Information Theory · Computer Science 2022-02-22 Jide Yuan , George C. Alexandropoulos , Eleftherios Kofidis , Tobias Lindstrm Jensen , Elisabeth De Carvalho

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

Extremely large-scale multiple-input multiple-output (XL-MIMO) is expected to be an important technology in future sixth generation (6G) networks. Compared with conventional single-polarized XL-MIMO, where signals are transmitted and…

Information Theory · Computer Science 2025-02-21 Shuhao Zeng , Boya Di , Hongliang Zhang , Zhu Han , H. Vincent Poor

Reconfigurable Intelligent Surface (RIS) technology has emerged as a key enabler for future wireless communications. However, its potential is constrained by the difficulty of acquiring accurate user-to-RIS channel state information (CSI),…

Signal Processing · Electrical Eng. & Systems 2026-04-20 Md. Shahriar Sadid , Ali A. Nasir , Saad Al-Ahmadi , Samir Al-Ghadhban

We investigate the performance of a multiple reconfigurable intelligence surface (RIS)-aided millimeter wave (mmWave) beamspace multiple-input multiple-output (MIMO) system with multiple users (UEs). We focus on a challenging scenario in…

Information Theory · Computer Science 2025-05-21 Zaid Abdullah , Mario R. Camana , Abuzar B. M. Adam , Chandan K. Sheemar , Eva Lagunas , Symeon Chatzinotas

The large bandwidth combined with ultra-massive multiple-input multiple-output (UM-MIMO) arrays enables terahertz (THz) systems to achieve terabits-per-second throughput. The THz systems are expected to operate in the near, intermediate, as…

Information Theory · Computer Science 2023-10-27 Simon Tarboush , Anum Ali , 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

Beyond diagonal reconfigurable intelligent surface (BD-RIS) is a new advance and generalization of the RIS technique. BD-RIS breaks through the isolation between RIS elements by creatively introducing inter-element connections, thereby…

Signal Processing · Electrical Eng. & Systems 2024-06-11 Hongyu Li , Shanpu Shen , Yumeng Zhang , Bruno Clerckx