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Near-field channel estimation for extremely large-scale Terahertz communications

Science China(Information Sciences) 2024年第9期67卷 213-228页

作者： Songjie YANG Yizhou PENG Wanting LYU Ya LI Hongjun HE Zhongpei ZHANG chau yuen National Key Laboratory of Wireless Communications University of Electronic Science and Technology of China Future Research Laboratory China Mobile Research Institute School of Electrical and Electronics Engineering Nanyang Technological University

Future Terahertz communications exhibit significant potential in accommodating ultra-high-rate services. Employing extremely large-scale array antennas is a key approach to realize this potential, as they can harness substantial beamforming gains to overcome the severe path loss and leverage the electromagnetic advantages in the near field. This paper proposes novel estimation methods designed to enhance efficiency in Terahertz widely-spaced multi-subarray(WSMS) systems. Initially, we introduce three sparse channel representation methods: polar-domain representation(PD-R), multi-angular-domain representation(MADR), and two-dimensional polar-angular-domain representation(2D-PAD-R). Each method is meticulously developed for near-field WSMS channels, capitalizing on their sparsity characteristics. Building on this,we propose four estimation frameworks using the sparse recovery theory: polar-domain estimation(PD-E),multi-angular-domain estimation(MAD-E), two-stage polar-angular-domain estimation(TS-PAD-E), and two-dimensional polar-angular-domain estimation(2D-PAD-E). Particularly, 2D-PAD-E, integrating a 2D dictionary process, and TS-PAD-E, with its sequential approach to angle and distance estimation, stand out as particularly effective for near-field angle-distance estimation, enabling decoupled calculation of these parameters. Overall, these frameworks provide versatile and efficient solutions for WSMS channel estimation,balancing low complexity with high-performance outcomes. Additionally, they represent a fresh perspective on near-field signal processing.

关键词： Terahertz communications near field channel estimation widely-spaced multi-subarray sparse recovery

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面向全息MIMO 6G通信的电磁信道建模理论与方法

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电子与信息学报 2024年第5期46卷 1940-1950页

作者：黄崇文季然魏丽宫铁瑞陈晓明沙威杨军张朝阳 yuen chau 浙江大学信息与电子工程学院杭州310027 新加坡科技与设计大学新加坡487372 西安交通大学信息与通信工程学院西安710049 中兴通讯股份有限公司深圳518000 新加坡南洋理工大学新加坡639798

全息多输入多输出(HMIMO)是6G通信中的新兴技术,相应阵列由固定物理孔径下的密布天线单元组成。全息MIMO是电磁约束下Massive MIMO天线技术的拓展。全息MIMO系统在有效提升无线通信性能方面具有极大的潜力。比如,可用最小的功率损耗实... 详细信息

全息多输入多输出(HMIMO)是6G通信中的新兴技术,相应阵列由固定物理孔径下的密布天线单元组成。全息MIMO是电磁约束下Massive MIMO天线技术的拓展。全息MIMO系统在有效提升无线通信性能方面具有极大的潜力。比如,可用最小的功率损耗实现尽可能大的连续孔径,灵活控制目标方向的电磁波传输等。但是,由于全息MIMO系统包含大量的紧密分布的天线单元,且单元之间的距离小于半波长,因而造成严重的电磁耦合作用。这些耦合使传统的独立同分布的信道假设失效。因此,如何设计一个有效且贴近实际的信道建模成为当前全息MIMO研究中最具挑战性的问题之一。针对该挑战,该文研究了基于电磁场理论的4种信道建模方式,它们都能很好描述全息MIMO系统中的电磁波传输特征。第1种是基于平面格林函数的精确信道建模方式,该方式将自由空间中点对点的格林函数扩展到平面之间积分形式的格林函数,通过积分计算来构造两个全息MIMO平面之间的通信信道,但该方法的复杂度较高。第2, 3种方法则分别采用了平面波展开和球面波展开来近似全息MIMO的通信信道,这两种方案的复杂度更低。其中,基于平面波展开的信道建模形式相对简单,更适用于远场,但是会低估单元强耦合时的最大系统容量;基于球面波展开的信道建模能更好捕捉电磁波信道几何特征,但其复杂度较高。最后介绍基于随机格林函数的信道建模方法,主要描述富散射环境或瑞利信道中电磁波的随机特性。

关键词：全息MIMO通信电磁波理论信道建模

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Reconfiguring wireless environments via intelligent surfaces for 6G: reflection, modulation, and security

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Science China(Information Sciences) 2023年第3期66卷 60-79页

作者： Jindan XU chau yuen Chongwen HUANG Naveed UL HASSAN George C.ALEXANDROPOULOS Marco DI RENZO Mérouane DEBBAH Engineering Product Development Pillar Singapore University of Technology and Design College of Information Science and Electronic Engineering Zhejiang University Department of Electrical Engineering Lahore University of Management Sciences Department of Informatics and Telecommunications National and Kapodistrian University of Athens Technology Innovation Institute Université Paris-Saclay CNRS Centrale Supélec Laboratoire des Signaux et Systèmes

The reconfigurable intelligent surface(RIS) has been recognized as an essential enabling technology for sixth-generation(6G) mobile communication networks. An RIS comprises a large number of small and low-cost reflecting elements whose parameters can be dynamically adjusted with a programmable *** of these elements can effectively reflect a phase-shifted version of the incident electromagnetic wave. By configuring the wave phases in real time, the propagation environment of the information-bearing signals can be dynamically manipulated to enhance communication reliability, boost transmission rate, expand cellular coverage, and strengthen communication security. In this study, we provide an overview on RIS-assisted wireless communications. Specifically, we elaborate on the state-of-the-art enabling techniques for the RIS technology as well as their corresponding substantial benefits from the perspectives of RIS reflection and RIS modulation. With these benefits, we envision the integration of RISs into emerging applications for6G. In addition, communication security is of unprecedented importance in future 6G networks with ubiquitous wireless services in multifarious verticals and areas. We highlight potential contributions of RISs to physical-layer security, in terms of secrecy rate and secrecy outage probability, exemplified by a typical case study from both theoretical and numerical aspects. Finally, we discuss challenges and opportunities on the deployment of RISs in practice to motivate future research.

关键词： reconfigurable intelligent surface physical-layer security RIS-assisted wireless communications phase modulation 6G

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Reconfigurable intelligent surfaces for wireless communications:Overview of hardware designs,channel models,and estimation techniques

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Intelligent and Converged Networks 2022年第1期3卷 1-32页

作者： Mengnan Jian George C.Alexandropoulos Ertugrul Basar Chongwen Huang Ruiqi Liu Yuanwei Liu chau yuen the Wireless Research Institute ZTE CorporationBeijing 100029China the State Key Laboratory of Mobile Network and Mobile Multimedia Technology Shenzhen 518055China Department of Informatics and Telecommunications National and Kapodistrian University of AthensAthens 15784Greece Communications Research and Innovation Laboratory(CoreLab) Department of Electrical and Electronics EngineeringKoçUniversityIstanbul 34450Turkey College of Information Science and Electronic Engineering Zhejiang UniversityHangzhou 310027China School of Electronic Engineering and Computer Science Queen Mary University of LondonLondonE14NSUK. the Engineering Product Development(EPD)Pillar Singapore University of Technology and DesignSingapore 487372Singapore

The demanding objectives for the future sixth generation(6G)of wireless communication networks have spurred recent research efforts on novel materials and radio-frequency front-end architectures for wireless connectivity,as well as revolutionary communication and computing *** the pioneering candidate technologies for 6G belong the reconfigurable intelligent surfaces(RISs),which are artificial planar structures with integrated electronic circuits that can be programmed to manipulate the incoming electromagnetic field in a wide variety of *** RISs in wireless networks have been recently advocated as a revolutionary means to transform any wireless signal propagation environment to a dynamically programmable one,intended for various networking objectives,such as coverage extension and capacity boosting,spatiotemporal focusing with benefits in energy efficiency and secrecy,and low electromagnetic field *** by the recent increasing interests in the field of RISs and the consequent pioneering concept of the RIS-enabled smart wireless environments,in this paper,we overview and taxonomize the latest advances in RIS hardware architectures as well as the most recent developments in the modeling of RIS unit elements and RIS-empowered wireless signal *** also present a thorough overview of the channel estimation approaches for RIS-empowered communications systems,which constitute a prerequisite step for the optimized incorporation of RISs in future wireless ***,we discuss the relevance of the RIS technology in the latest wireless communication standards,and highlight the current and future standardization activities for the RIS technology and the consequent RIS-empowered wireless networking approaches.

关键词： reconfigurable intelligent surfaces beyond 5G 6G channel modeling hardware architecture channel estimation smart wireless environment standardization

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Energy-efficient spectrum-aware clustering for cognitive radio sensor networks

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Chinese Science Bulletin 2012年第28期57卷 3731-3739页

作者： ZHANG HuaZi ZHANG ZhaoYang yuen chau Department of Information Science and Electronic Engineering Zhejiang UniversityHangzhou 310027China Zhejiang Provincial Key Laboratory of Information Network Technology Hangzhou 310027China Singapore University of Technology and Design Singapore

As a smart combination of cognitive radio networks and wireless sensor networks,recently introduced cognitive radio sensor network(CRSN) poses new challenges to the design of topology maintenance techniques for dynamic primary-user *** paper aims to provide a solution to the energy-efficient spectrum-aware CRSN clustering ***,we design the clustered structure,establish a network-wide energy consumption model and determine the optimal number of *** then employ the ideas from constrained clustering and propose both a centralized spectrum-aware clustering algorithm and a distributed spectrum-aware clustering(DSAC) *** extensive simulations,we demonstrate that DSAC can effectively form clusters under a dynamic spectrum-aware ***,DSAC exhibits preferable scalability and stability with its low complexity and quick convergence under dynamic spectrum variation.

关键词：无线传感器网络认知无线电频谱感知集群节能高效聚类问题无线电网络

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Resource Allocation for Two-Tier RIS-Assisted Heterogeneous NOMA Networks

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ZTE Communications 2022年第1期20卷 36-47页

作者： XU Yongjun YANG Zhaohui HUANG Chongwen yuen chau GUI Guan School of Communication and Information Engineering Chongqing University of Posts and TelecommunicationsChongqing 400065China Department of Electronic and Electrical Engineering University College LondonLondon WC1E 6BTUK College of Information Science and Electronic Engineering Zhejiang UniversityHangzhou 310027China Engineering Product Development Pillar Singapore University of Technology and DesignSingapore 487372Singapore College of Telecommunications and Information Engineering Nanjing University of Posts and TelecommunicationsNanjing 210003China

Reconfigurable intelligent surface(RIS)as a promising technology has been proposed to change weak communication ***,most of the current resource allocation(RA)schemes have focused on RIS-assisted homogeneous networks,and there is still no open works about RA schemes of RIS-assisted heterogeneous networks(HetNets).In this paper,we design an RA scheme for a RIS-assisted HetNet with non-orthogonal multiple access to improve spectrum efficiency and transmission *** particular,we jointly optimize the transmit power of the small-cell base station and the phase-shift matrix of the RIS to maximize the sum rates of all small-cell users,subject to the unit modulus constraint,the minimum signal-to-interference-plus-noise ratio constraint,and the cross-tier interference constraint for protecting communication quality of microcell *** efficient suboptimal RA scheme is proposed based on the alternating iteration ap-proach,and successive convex approximation and logarithmic transformation *** results verify the effectiveness of the pro-posed scheme in terms of data rates.

关键词： heterogeneous networks non-orthogonal multiple access reconfigurable intelligent surface resource allocation

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AI-EMPOWERED MILLIMETER WAVE COMMUNICATION AND NETWORKING

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China Communications 2020年第10期17卷 97-99页

作者： Wenjun Xu Chuan Huang Yongming Huang chau yuen Shuguang Cui Beijing Univ Posts & Telecommun BUPT Sch Artificial Intelligence Beijing Peoples R China Minist Educ Key Lab Universal Wireless Commun Beijing Peoples R China Arizona State Univ Tempe AZ USA Princeton Univ Princeton NJ 08544 USA Chinese Univ Hong Kong Shenzhen Hong Kong Peoples R China Southeast Univ Sch Informat Sci & Engn Nanjing Peoples R China Lucent Technol Bell Labs Murray Hill NJ USA Inst Infocomm Res I2R Singapore Singapore Singapore Univ Technol & Design Singapore Singapore Univ Arizona Elect & Comp Engn Tucson AZ 85721 USA Texas A&M Univ College Stn TX 77843 USA Univ Calif Davis Davis CA USA CUHK Shenzhen Peoples R China Shenzhen Res Inst Big Data Shenzhen Peoples R China

Thanks to the abundant and attractive spectrum resource in the millimeter-wave(mmWave)band,mmWave technologies have been widely applied to the fifth-generation(5G)mobile communication system and will continuously evolve towards the future beyond 5G systems as ***,achieving the pervasive application of mmWave for 5G and beyond still faces many challenges,for example,the severe path-loss and vulnerability in blockage of mmWave propagation may have a great impact on mmWave communication and networking.

关键词： beyond communication millimeter

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Wireless communications empowered by reconfigurable intelligent surfaces: Model-based vs model-free channel estimation

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Journal of Information and Intelligence 2023年第3期1卷 253-266页

作者： Li Wei Chongwen Huang George C.Alexandropoulos Ahmet M.Elbir Zhaohui Yang Zhaoyang Zhang Marco Di Renzo Merouane Debbah chau yuen Engineering Product Development Pillar Singapore University of Technology and DesignSingapore 487372Singapore College of Information Science and Electronic Engineering Zhejiang UniversityHangzhou 310027China Department of Informatics and Telecommunications National and Kapodistrian University of Athens15784 AthensGreece Interdisciplinary Centre for Security Reliability and TrustUniversity of LuxembourgL-4365 Esch-sur-AlzetteLuxembourgand Duzce UniversityDuzce 81620Turkey Universite Paris-Saclay CNRSCentraleSupelecLaboratoire des Signaux et Systemes91192France Khalifa University of Science and Technology Abu DhabiUnited Arab Emirates School of Electrical and Electronics Engineering Nanyang Technological UniversitySingapore 639798Singapore

Reconfigurable intelligent surfaces(RISs)are lately being attractive for their great potential in future sixth generation wireless communications(6G),which is attributed to their affordable energy consumption and easy ***,the large numbers of low-cost reflecting elements comprising RISs impose challenges for channel acquisition in various RIS-based wireless applications,such as RIS-enhanced orthogonal frequency-division multiplexing and multi-user multipleinput multiple-output *** this article,we first overview the state-of-the-art RIS hardware architectures designed to assist channel estimation for RIS-empowered wireless communication *** also overview existing channel estimation approaches,which are categorized into model-based and model-free techniques,and discuss their advantages and limitations depending on the RIS *** challenges with RIS-empowered systems in terms of hardware and other parameter limitations are presented,together with future research directions for channel estimation in RIS-based wireless systems,such as RISs with extremely large numbers of elements,multi-hop communications with RISs,and frequency division duplexing for high mobility systems.

关键词： Reconfigurable intelligent surfaces Channel estimation Model-based methods Model-free methods

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Palladium-Catalyzed Desulfinative Cross-Coupling of Polyhalogenated Aryl Triflates with Aryl Sulfinate Salts:Inversion of Traditional Chemoselectivity

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Chinese Journal of Chemistry 2023年第8期41卷 909-914页

作者： Miao Wang On Ying yuen chau Ming So State Key Laboratory of Chemical Biology and Drug Discovery and Department of Applied Biology and Chemical Technology The Hong Kong Polytechnic UniversityKowloonHong KongChina Henan Key Laboratory of Function-Oriented Porous Materials College of Chemistry and Chemical EngineeringLuoyang Normal UniversityLuoyangHenan471934 China The Hong Kong Polytechnic University Shenzhen Research Institute ShenzhenGuangdong518057 China

Comprehensive Summary This paper presents the first general examples of palladium-catalyzed desulfinative cross-coupling reaction of polyhalogenated aryl triflates with aryl sulfinate salts showing an inversion of the conventional reactivity order of C-Br>C-Cl>*** catalyst system,comprising of Pd(OAc)_(2)and tBuPhSelectPhos,exhibited excellent catalytic reactivity and chemoselectivity toward this *** reaction had a wide range of substrate scopes and provided a simple and efficient method for the construction of functionalized biaryl ***,the C-H···Pd interaction from the methine hydrogen of the C2-cyclohexyl group of the indolyl phosphine ligand with the Pd center may contribute a key factor in reactivity and *** with density functional theory(DFT)calculations,the results revealed that the oxidative addition step in this reaction was a controlling-chemoselectivity step.

关键词： Palladium Phosphane ligands IChemoselectivity Desulfurization Polyhalogenated aryl triflates

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Energy-efficient spectrum-aware clustering for cognitive radio sensor networks

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Science Bulletin 2012年第Z2期 3731-3739页

作者： ZHANG HuaZi 1,2,ZHANG ZhaoYang 1,2* & yuen chau 3 1 Department of Information Science and Electronic Engineering,Zhejiang University,Hangzhou 310027,China 2 Zhejiang Provincial Key Laboratory of Information Network Technology,Hangzhou 310027,China 3 Singapore University of Technology and Design,Singapore

关键词： cognitive radio sensor network constrained clustering energy efficient distributed spectrum-aware clustering

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