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The demand for unprecedented performance in the upcoming 6G wireless networks is fomenting the research on THz communications empowered by Reconfigurable Inteligent Surfaces (RISs). A wide range of use cases have been proposed, most of…

Reconfigurable intelligent surface (RIS) is envisioned to be a promising green technology to reduce the energy consumption and improve the coverage and spectral efficiency of massive multiple-input multiple-output (MIMO) wireless networks.…

Information Theory · Computer Science 2021-02-12 Zhen-Qing He , Hang Liu , Xiaojun Yuan , Ying-Jun Angela Zhang , Ying-Chang Liang

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

A reconfigurable intelligent surface (RIS) can shape the radio propagation environment by virtue of changing the impinging electromagnetic waves towards any desired directions, thus, breaking the general Snell's reflection law. However, the…

Signal Processing · Electrical Eng. & Systems 2021-01-15 Jiguang He , Henk Wymeersch , Markku Juntti

Terahertz (THz) communication offers ultra-high data rates and has emerged as a promising technology for future wireless networks. However, the inherently high free-space path loss of THz waves significantly limits the coverage range of THz…

Signal Processing · Electrical Eng. & Systems 2025-12-17 Ben Chen , Zhangdui Zhong , Ke Guan , Danping He , Yiran Wang , Jianwen Ding , Qi Luo

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

Intelligent reflecting surface (IRS)-assisted full-duplex (FD) terahertz (THz) communication systems have emerged as a promising paradigm to satisfy the escalating demand for ultra-high data rates and spectral efficiency in future wireless…

Information Theory · Computer Science 2025-10-30 Chi Qiu , Wen Chen , Qingqing Wu , Fen Hou , Wanming Hao , Ruiqi Liu , Derrick Wing Kwan Ng

Pixel-based reconfigurable intelligent surfaces (RISs) employ a novel design to achieve high reflection gain at a lower hardware cost by eliminating the phase shifters used in traditional RIS. However, this design presents challenges for…

Signal Processing · Electrical Eng. & Systems 2025-10-24 Huayan Guo , Junhui Rao , Alex M. H. Wong , Ross Murch , Vincent K. N. Lau

Wireless communications in the THz frequency band is an envisioned revolutionary technology for sixth Generation (6G) networks. However, such frequencies impose certain coverage and device design challenges that need to be efficiently…

Networking and Internet Architecture · Computer Science 2024-03-14 George C. Alexandropoulos , Antonio Clemente , Sérgio Matos , Ryan Husbands , Sean Ahearne , Qi Luo , Verónica Lain-Rubio , Thomas Kürner , Luís M. Pessoa

The transition to Terahertz (THz) frequencies, providing an ultra-wide bandwidth, is a key driver for future wireless communication networks. However, the specific properties of the THz channel, such as severe path loss and vulnerability to…

Information Theory · Computer Science 2024-01-26 Yasemin Karacora , Adam Umra , Aydin Sezgin

Novel reconfigurable intelligent surface (RIS) architectures, known as beyond diagonal RISs (BD-RISs), have been proposed to enhance reflection efficiency and expand RIS capabilities. However, their passive nature, non-diagonal reflection…

Signal Processing · Electrical Eng. & Systems 2024-11-28 Nipuni Ginige , Arthur Sousa de Sena , Nurul Huda Mahmood , Nandana Rajatheva , Matti Latva-aho

This paper considers wireless communication assisted by a reconfigurable intelligent surface (RIS), focusing on the two-timescale approach, in which the RIS phase shifts are optimized based on channel statistics to mitigate the overheads…

Information Theory · Computer Science 2025-07-30 Masoud Sadeghian , Angel Lozano , Gabor Fodor

Intelligent reflecting surface (IRS) has drawn a lot of attention recently as a promising new solution to achieve high spectral and energy efficiency for future wireless networks. By utilizing massive low-cost passive reflecting elements,…

Information Theory · Computer Science 2022-10-17 Ming-Min Zhao , Qingqing Wu , Min-Jian Zhao , Rui Zhang

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

Rate splitting multiple access (RSMA) and reconfigurable intelligent surface (RIS) are two prospective technologies for improving the spectral and energy efficiency in future wireless communication systems. In this work, we investigate a…

Signal Processing · Electrical Eng. & Systems 2024-10-17 Sadaf Syed , Michael Joham , Wolfgang Utschick

Optimally extracting the advantages available from reconfigurable intelligent surfaces (RISs) in wireless communications systems requires estimation of the channels to and from the RIS. The process of determining these channels is…

Information Theory · Computer Science 2021-10-04 A. Lee Swindlehurst , Gui Zhou , Rang Liu , Cunhua Pan , Ming Li

Reconfigurable intelligent surfaces (RIS) can be crucial in next-generation communication systems. However, designing the {RIS} phases according to the instantaneous channel state information (CSI) can be challenging in practice due to the…

Information Theory · Computer Science 2023-09-26 Athira Subhash , Abla Kammoun , Ahmed Elzanaty , Sheetal Kalyani , Yazan H. Al-Badarneh , Mohamed-Slim Alouini

Intelligent reflecting surface (IRS) is a promising technology to improve the performance of backscatter communication systems by smartly reconfiguring the multi-reflection channel. To fully exploit the passive beamforming gain of IRS in…

Information Theory · Computer Science 2021-03-17 Samith Abeywickrama , Changsheng You , Rui Zhang , Chau Yuen

Existing research works on reconfigurable intelligent surfaces (RIS) based terahertz (THz) system ignores the effect of phase noise and employ the zero-boresight pointing errors model of the free-space optics channel in performance…

Information Theory · Computer Science 2022-11-17 Omkar R. Durgada , Vinay Kumar Chapala , S. M. Zafaruddin

This chapter focuses on a hardware architecture for semi-passive Reconfigurable Intelligent Surfaces (RISs) and investigates its consideration for boosting the performance of Multiple-Input Multiple-Output (MIMO) communication systems. The…

Signal Processing · Electrical Eng. & Systems 2025-06-19 George C. Alexandropoulos , Konstantinos D. Katsanos , Evangelos Vlachos