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Reconfigurable Intelligent Surfaces (RIS) are passive or semi-passive heterogeneous metasurfaces and consist of many tunable elements. RIS is gaining momentum as a promising new technology to enable transforming the propagation environment…

Signal Processing · Electrical Eng. & Systems 2022-01-06 Pooja Nuti , Elyes Balti , Brian L. Evans

For downlink massive multiple-input multiple-output (MIMO) operating in time-division duplex protocol, users can decode the signals effectively by only utilizing the channel statistics as long as channel hardening holds. However, in a…

Information Theory · Computer Science 2022-05-17 Tung T. Vu , Trinh Van Chien , Canh T. Dinh , Hien Quoc Ngo , Michail Matthaiou

In this paper, we consider an active reconfigurable intelligent surface (RIS) to assist the multiuser downlink transmission in the presence of practical hardware impairments (HWIs), including the HWIs at the transceivers and the phase noise…

Signal Processing · Electrical Eng. & Systems 2024-02-19 Zhangjie Peng , Zhibo Zhang , Cunhua Pan , Marco Di Renzo , Octavia A. Dobre , Jiangzhou Wang

An unmanned surface vehicle (USV) can perform complex missions by continuously observing the state of its surroundings and taking action toward a goal. A SWARM of USVs working together can complete missions faster, and more effectively than…

Robotics · Computer Science 2024-09-02 Shrudhi R S , Sreyash Mohanty , Susan Elias

This letter focuses on a transmitter or base station (BS) side beyond-diagonal reflecting intelligent surface (BD-RIS) deployment strategy to enhance the spectral efficiency (SE) of a time-division-duplex massive multiple-input…

Information Theory · Computer Science 2023-07-20 Anup Mishra , Yijie Mao , Carmen D'Andrea , Stefano Buzzi , Bruno Clerckx

In this work, in order to achieve higher spectrum efficiency, we propose a reconfigurable intelligent surface (RIS)-assisted multi-user communication uplink system. Different from previous work in which the RIS only optimizes the phase of…

Information Theory · Computer Science 2020-11-19 Liang Yang , Fanxu Meng , Mazen O. Hasna , Ertugrul Basar

Recently, intelligent reflecting surface (IRS) has emerged as an appealing technique that enables wireless communications with low hardware cost and low power consumption. In this letter, we consider an IRS-assisted point-to-point…

Information Theory · Computer Science 2020-04-17 Boyu Ning , Zhi Chen , Wenjie Chen , Jun Fang

Reducing computational complexity is crucial in optimizing the phase shifts of Intelligent Reflecting Surface (IRS) systems since IRS-assisted communication systems are generally deployed with a large number of reflecting elements (REs).…

Information Theory · Computer Science 2022-04-12 Ahmad Sirojuddin , Dony Darmawan Putra , Wan-Jen Huang

This work considers a reconfigurable intelligent surface (RIS)-aided cell-free massive multiple-input multiple-output (MIMO) system with RIS spatial correlation and electromagnetic interference (EMI). We propose a two-phase channel…

Information Theory · Computer Science 2024-11-18 Jun Qian , Chi Zhang , Khaled B. Letaief , Ross Murch

This paper investigates the downlink power allocation of the simultaneous transmitting and reflecting reconfigurable intelligent surface (STAR-RIS)-assisted cell-free massive multiple-input multiple-output (MIMO) system with multi-antenna…

Information Theory · Computer Science 2025-12-23 Jun Qian , Ross Murch , Khaled B. Letaief

In this paper, we propose reconfigurable intelligent surface (RIS)-assisted unmanned aerial vehicles (UAVs) networks that can utilise both advantages of UAV's agility and RIS's reflection for enhancing the network's performance. To aim at…

Signal Processing · Electrical Eng. & Systems 2021-08-09 Khoi Khac Nguyen , Saeed Khosravirad , Daniel Benevides da Costa , Long D. Nguyen , Trung Q. Duong

Although reconfigurable intelligent surface (RIS) is a promising technology for shaping the propagation environment, it consists of a single-layer structure within inherent limitations regarding the number of beam steering patterns. Based…

In this paper, a novel network architecture that deploys the multi-functional reconfigurable intelligent surface (MF-RIS) in low-Earth orbit (LEO) is proposed. Unlike traditional RIS with only signal reflection capability, the MF-RIS can…

Machine Learning · Computer Science 2025-11-18 Li-Hsiang Shen , Jyun-Jhe Huang , Kai-Ten Feng , Lie-Liang Yang , Jen-Ming Wu

In this letter, we present in detail the system-level modeling of reconfigurable intelligent surface (RIS)-assisted cellular systems by considering a 3-dimensional channel model between base station, RIS, and user. We prove that the optimal…

Information Theory · Computer Science 2023-05-03 Pavan Reddy M. , SaiDhiraj Amuru , Kiran Kuchi

An integration of satellites and terrestrial networks is crucial for enhancing performance of next generation communication systems. However, the networks are hindered by the long-distance path loss and security risks in dense urban…

Signal Processing · Electrical Eng. & Systems 2025-12-25 Chuang Zhang , Geng Sun , Jiahui Li , Jiacheng Wang , Ruichen Zhang , Dusit Niyato , Shiwen Mao , Abbas Jamalipour

In this paper, the problem of maximizing the sum-rate is addressed for a multi-user uplink scenario that is assisted by an active reconfigurable intelligent surface (RIS). The maximization is achieved by optimizing the beamforming at the…

Signal Processing · Electrical Eng. & Systems 2026-04-06 Mohamed Shalma , Engy Maher , Ahmed El-Mahdy

In this paper, we focus on the sum-rate optimization in a multi-user millimeter-wave (mmWave) system with distributed intelligent reflecting surfaces (D-IRSs), where a base station (BS) communicates with users via multiple IRSs. The BS…

Signal Processing · Electrical Eng. & Systems 2021-01-22 Yue Xiu , Wei Sun , Jiao Wu , Guan Gui , Ning Wei , Zhongpei Zhang

Beamforming design with partial channel estimation and feedback for frequency-division duplexing (FDD) reconfigurable intelligent surface (RIS) assisted systems is considered in this paper. We leverage the observation that path angle…

Signal Processing · Electrical Eng. & Systems 2025-06-03 Xiaochun Ge , Shanping Yu , Wenqian Shen , Chengwen Xing , Byonghyo Shim

Hybrid reconfigurable intelligent surfaces (HRIS) enhance wireless systems by combining passive reflection with active signal amplification. However, jointly optimizing the transmit beamforming with the HRIS reflection and amplification…

Signal Processing · Electrical Eng. & Systems 2026-04-13 Phuong Nam Tran , Nhan Thanh Nguyen , Markku Juntti

The integration of low earth orbit (LEO) satellites with terrestrial communication networks holds the promise of seamless global connectivity. The efficiency of this connection, however, depends on the availability of reliable channel state…

Signal Processing · Electrical Eng. & Systems 2025-05-13 Yasaman Omid , Marios Aristodemou , Sangarapillai Lambotharan , Mahsa Derakhshani , Lajos Hanzo