In this paper, we investigate a non-lineof-sight (NLOS) sensing problem at terahertz frequencies. To be able to observe the targets shadowed by a blockage, we propose a method using reconfigurable intelligent surfaces (RIS). We employ a bistatic radar system and scan the obstructed area with RIS using hierarchical codebooks (HCB). Moreover, we propose an iterative maximum likelihood estimation (MLE) scheme to yield the optimum sensing accuracy, converging to Cramer-Rao lower bound (CRLB). We take band-specific effects such as diffraction and beam squint into account and show that these effects are relevant factors affecting localization performance in RIS-employed radar setups. The results show that under NLOS conditions, the system can still localize all the targets with very good accuracy using the RIS. The initial estimates obtained by the HCBs can provide centimeter-level accuracy, and when the optimal performance is needed, at the cost of a few extra transmissions, the proposed iterative MLE method improves the accuracy to sub-millimeter accuracy, yielding the position error bound.
Beyond $λ/2$: Can Arbitrary EMVS Arrays Achieve Unambiguous NLOS Localization?
Ningbo University（宁波大学）；South China University of Technology（华南理工大学）；The Hong Kong Polytechnic University（香港理工大学）；Queen Mary University of London（伦敦大学玛丽女王学院）；Kyung Hee University（庆熙大学）；West Virginia University（西弗吉尼亚大学）
Low Earth Orbit (LEO) satellite communications (SatCom) are considered a promising solution to provide uninterrupted services in cellular networks. Line-of-sight (LoS) links between the LEO satellites and the ground users are, however, easily blocked in urban scenarios. In this paper, we propose to enable LEO SatCom in non-line-of-sight (NLoS) channels, as those corresponding to links to users in urban canyons, with the aid of reconfigurable intelligent surfaces (RISs). First, we derive the near field signal model for the satellite-RIS-user link. Then, we propose two deployments to improve the…
We propose a metric called the bistatic radar detection coverage probability to evaluate the detection performance of a bistatic radar under discrete clutter conditions. Such conditions are commonly encountered in indoor and outdoor environments where passive radars receivers are deployed with opportunistic illuminators. Backscatter and multipath from the radar environment give rise to ghost targets and point clutter responses in the radar signatures resulting in deterioration in the detection performance. In our work, we model the clutter points as a Poisson point process to account for the d…
Near-Field NLOS Localization via Position-Unknown HRIS:From Self-Localization to Target Positioning
Ningbo University（宁波大学）；South China University of Technology（华南理工大学）；Queen Mary University of London（伦敦玛丽女王大学）；The University of Texas at Dallas（德克萨斯大学达拉斯分校）；Khalifa University（哈利法大学）；University of Missouri（密苏里大学）
A Robust Two-Stage Protocol for STAR-RIS-Aided ISAC Networks: Joint Beamforming and Mode Optimization
College of Information and Communication Engineering of Harbin Engineering University（哈尔滨工程大学信息与通信工程学院）；Department of Electrical Engineering and Information Technology, University Federico II（那不勒斯费德里科二世大学电气与信息工程系）；Fields & Waves Lab, Department of Engineering, University of Sannio（桑尼奥大学工程系场与波实验室）；Department of Engineering, University of Campania Luigi Vanvitelli（坎帕尼亚路易吉范维泰利大学工程系）
Reconfigurable Intelligent Surface (RIS) is a planar array that can control reflection and thus can implement the concept of partially controllable propagation environment. RIS received a lot of attention from industry and academia, but the majority of the researchers who study RIS-assisted systems use simple Rician model. Though it is suitable for theoretical analysis, stochastic Non Line-of-Sight (NLoS) component in Rician model does not account for the geometry of deployment. Furthermore, Rician model is not eligible to evaluate 3GPP standardization proposals. In this article we adapt the p…
A Miniaturized Broadband 1-Bit Coding Reconfigurable Intelligent Surface for NLOS UE Localization and Uplink Communication
Indraprastha Institute of Information Technology Delhi（德里信息技术学院）；Indian Institute of Technology Roorkee（印度理工学院鲁尔基分校）；Vellore Institute of Technology（维洛尔理工学院）；Indian Institute of Technology Delhi（印度理工学院德里分校）
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). The RISs have been of great interest lately to maximize the channel gains in non-line-of-sight (NLOS) communication situations. We derive expressions for stochastic interference level in RIS powered systems and validate those with simulations. It will be shown that the interference levels via RIS link are rather small compared to the designed RIS link or the L…
A reconfigurable intelligent surface (RIS) is a nearly-passive flat layer made of inexpensive elements that can add a tunable phase shift to the impinging electromagnetic wave and are controlled by a low-power electronic circuit. This paper considers the fundamental problem of target detection in a RIS-aided multiple-input multiple-output (MIMO) radar. At first, a general signal model is introduced, which includes the possibility of using up to two RISs (one close to the radar transmitter and one close to the radar receiver) and subsumes both a monostatic and a bistatic radar configuration wit…
Reconfigurable intelligent surface (RIS)-aided wireless communications have drawn significant attention recently. We study the physical layer security of the downlink RIS-aided transmission framework for randomly located users in the presence of a multi-antenna eavesdropper. To show the advantages of RIS-aided networks, we consider two practical scenarios: Communication with and without RIS. In both cases, we apply the stochastic geometry theory to derive exact probability density function (PDF) and cumulative distribution function (CDF) of the received signal-to-interference-plus-noise ratio.…
Near-optimal Reconfigurable Intelligent Surface Configuration: Blind Beamforming with Sensing
Warwick Manufacturing Group, University of Warwick（华威制造集团，华威大学）；Department of Computer Science, University of Warwick（华威大学计算机系）；Inria Centre at the University of Lille（里尔大学Inria中心）
