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LC technology is a promising hardware solution for realizing extremely large RISs due to its advantages in cost-effectiveness, scalability, energy efficiency, and continuous phase shift tunability. However, the slow response time of the LC…

Signal Processing · Electrical Eng. & Systems 2026-04-30 Mohamadreza Delbari , Robin Neuder , Alejandro Jiménez-Sáez , Arash Asadi , Vahid Jamali

Reconfigurable intelligent surfaces (RISs) have emerged as a key technology for dynamically reshaping wireless propagation, enhancing coverage and mitigating blockages to enable more pervasive network connectivity. However, implementing…

Signal Processing · Electrical Eng. & Systems 2026-04-22 Luis F. Abanto-Leon , Robin Neuder , Waqar Ahmed , Alejandro Jimenez Saez , Vahid Jamali , Arash Asadi

Liquid crystal (LC) is a promising hardware solution for implementing large RISs, as it is cost-effective, energy efficient, scalable, and capable of providing continuous phase shifts with low power consumption. However, the phase shift…

Signal Processing · Electrical Eng. & Systems 2026-04-22 Mohamadreza Delbari , Robin Neuder , Alejandro Jiménez-Sáez , Qikai Zhou , Vahid Jamali

To enhance coverage and signal quality in millimeter-wave (mmWave) frequencies, reconfigurable intelligent surfaces (RISs) have emerged as a game-changing solution to manipulate the wireless environment. Traditional semiconductor-based RISs…

Signal Processing · Electrical Eng. & Systems 2025-12-18 Le Hao , Robin Neuder , Mohamadreza Delbari , Alejandro Jiménez-Sáez , Vahid Jamali , Arash Asadi , Andrea Ortiz

Liquid crystal (LC) technology enables low-power and cost-effective solutions for implementing the reconfigurable intelligent surface (RIS). However, the phase-shift response of LC-RISs is temperature-dependent, which, if unaddressed, can…

Signal Processing · Electrical Eng. & Systems 2025-10-07 Mohamadreza Delbari , Bowu Wang , Nairy Moghadas Gholian , Arash Asadi , Vahid Jamali

Liquid crystal (LC) technology provides a low-power and scalable approach to implement a reconfigurable intelligent surface (RIS). However, the LC-based RIS's phase-shift response is inherently frequency-dependent, which can lead to…

Signal Processing · Electrical Eng. & Systems 2025-08-07 Mohamadreza Delbari , Qikai Zhou , Robin Neuder , Alejandro Jiménez-Sáez , Vahid Jamali

Liquid crystal (LC) technology has emerged as a promising solution for large reconfigurable intelligent surfaces (RISs) at millimeter wave (mmWave) bands, offering advantages such as low power consumption, scalability, and continuously…

Signal Processing · Electrical Eng. & Systems 2025-08-18 Bowu Wang , Mohamadreza Delbari , Robin Neuder , Alejandro Jiménez-Sáez , Vahid Jamali

With the surge of theoretical work investigating Reconfigurable Intelligent Surfaces (RISs) for wireless communication and sensing, there exists an urgent need of hardware solutions for the evaluation of these theoretical results and…

Information Theory · Computer Science 2023-08-08 Alejandro Jiménez-Sáez , Arash Asadi , Robin Neuder , Mohamadreza Delbari , Vahid Jamali

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

This paper presents the design, fabrication, and characterization of broadband liquid crystal (LC) reconfigurable intelligent surfaces (RIS) operating around 60 GHz and scaling up to 750 radiating elements. The RISs employ a delay line…

Signal Processing · Electrical Eng. & Systems 2026-01-19 Julia Schwarzbeck , Robin Neuder , Marc Späth , Alejandro Jiménez-Sáez

Until now, researchers in wireless communications have mainly focused their attention on slowly time-varying designs of reconfigurable intelligent surfaces (RISs), where the spatial-phase gradient across the RIS is varied at the rate equal…

Signal Processing · Electrical Eng. & Systems 2024-01-30 Francesco Verde , Donatella Darsena , Vincenzo Galdi

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

Reconfigurable intelligent surfaces (RIS), recognized as a critical enabler for 6G networks, exhibit unprecedented capabilities in electromagnetic wave manipulation and wireless channel reconfiguration. By leveraging existing network…

Information Theory · Computer Science 2025-08-19 Wenjun Teng , Weicong Chen , Yiping Zuo , Wankai Tang , Shi Jin

The reflecting antenna elements in most reconfigurable intelligent surfaces (RISs) use semiconductor-based (e.g., positive-intrinsic-negative (PIN) diodes and varactors) phase shifters. Although effective, a drawback of this technology is…

Signal Processing · Electrical Eng. & Systems 2025-05-09 Nairy Moghadas Gholian , Mohamadreza Delbari , Vahid Jamali , Arash Asadi

We introduce a phase hopping scheme for reconfigurable intelligent surfaces (RISs) in which the phases of the individual RIS elements are randomly varied with each transmitted symbol. This effectively converts slow fading into fast fading.…

Information Theory · Computer Science 2022-11-15 Karl-Ludwig Besser , Eduard A. Jorswieck

Reconfigurable intelligent surfaces (RISs) have emerged as a promising solution that can provide dynamic control over the propagation of electromagnetic waves. The RIS technology is envisioned as a key enabler of sixth-generation networks…

Signal Processing · Electrical Eng. & Systems 2025-02-26 Ishan Koralege , Arthur S. de Sena , Nurul H. Mahmood , Farjam Karim , Dimuthu Lesthuruge , Samitha Gunarathne

Reconfigurable intelligent surfaces (RIS) have been actively researched as a potential technique for future wireless communications, which intelligently ameliorate the signal propagation environment. In the conventional design, each RIS…

Information Theory · Computer Science 2022-03-17 Qingchao Li , Mohammed El-Hajjar , Ibrahim Hemadeh , Arman Shojaeifard , Alain A. M. Mourad , Bruno Clerckx , Lajos Hanzo

This article presents a novel approach of using reconfigurable intelligent surfaces (RISs) in the transmitter of indoor visible light communication (VLC) systems to enhance data rate uniformity and maintain adequate illumination. In this…

Signal Processing · Electrical Eng. & Systems 2023-08-22 Sylvester Aboagye , Telex M. N. Ngatched , Alain R. Ndjiongue , Octavia A. Dobre , Hyundong Shin

Reconfigurable intelligent surfaces (RISs) are a promising solution to improve the coverage of cellular networks, thanks to their ability to steer impinging signals in desired directions. However, they introduce an overhead in the…

Signal Processing · Electrical Eng. & Systems 2024-03-21 Anna V. Guglielmi , Stefano Tomasin

The adoption of a Reconfigurable Intelligent Surface (RIS) for downlink multi-user communication from a multi-antenna base station is investigated in this paper. We develop energy-efficient designs for both the transmit power allocation and…

Information Theory · Computer Science 2022-06-23 Chongwen Huang , Alessio Zappone , George C. Alexandropoulos , Mérouane Debbah , Chau Yuen
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