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RIS-Assisted Cell Free MIMO: A Survey

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ZTE Communications 2024年

作者： ZHAO Yaqiong KE Hongqin XU Wei YE Xinquan chen yijian National Mobile Communications Research Laboratory Southeast University Purple Mountain Laboratories ZTE Corporation

Cell-free (CF) multiple-input multiple-output (MIMO) is a promising technique to enable the vision of ubiquitous wireless connectivity for next-generation network communications. Compared to traditional co-located massive MIMO， CF MIMO allows geographically distributed access points (APs) to serve all users on the same time-frequency resource with spatial multiplexing techniques， resulting in better performance in terms of both spectral efficiency and coverage enhancement. However， the performance gain is achieved at the expense of deploying more APs with high cost and power consumption. To address this issue， the recently proposed reconfigurable intelligent surface (RIS) technique stands out with its unique advantages of low cost， low energy consumption and programmability. In this paper， we provide an overview of RIS-assisted CF MIMO and its interaction with advanced optimization designs and novel applications. Particularly， recent studies on typical performance metrics such as energy efficiency (EE) and spectral efficiency (SE) are surveyed. Besides， the application of RIS-assisted CF MIMO technique within various future communication systems is also envisioned. Additionally， we briefly discuss the technical challenges and open problems for this area to inspire research direction and fully exploit its potential in meeting the demands of future wireless communication systems.

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Degree of Freedom Analysis for Holographic MIMO Based on a Mutual-Coupling-Compliant Channel Model

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ZTE Communications 2024年第1期22卷 34-40页

作者： SUN Yunqi JIAN Mengnan YANG Jun ZHAO Yajun chen yijian State Key Laboratory of Mobile Network and Mobile Multimedia Technology Shenzhen 518055China ZTE Corporation Shenzhen 518057China

Degree of freedom(DOF)is a key indicator for spatial multiplexing layers of a wireless channel.Traditionally,the channel of a multiple-input multiple-output(MIMO)half-wavelength dipole array has a DOF that equals the antenna number.However,recent studies suggest that the DOF could be less than the antenna number when strong mutual coupling is considered.We utilize a mutual-coupling-compliant channel model to investigate the DOF of the holographic MIMO(HMIMO)channel and give a upper bound of the DOF with strong mutual coupling.Our numerical simulations demonstrate that a dense array can support more DOF per unit aperture as compared with a half-wavelength MIMO system.

关键词： channel model degree of freedom holographic MIMO mutual coupling

Degree of Freedom Analysis for Holographic MIMO Based on a Mutual-Coupling-Compliant Channel Model

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ZTE Communications 2024年

作者： SUN Yunqi JIAN Mengnan YANG Jun ZHAO Yajun chen yijian State Key Laboratory of Mobile Network and Mobile Multimedia Technology ZTE Corporation

Degree of freedom (DOF) is a key indicator for spatial multiplexing layers of a wireless channel. Traditionally， the channel of a multiple-input multiple-output (MIMO) half-wavelength dipole array has a DOF that equals the antenna number. However， recent studies suggest that the DOF could be less than the antenna number when strong mutual coupling is considered. We utilize a mutual-coupling-compliant channel model to investigate the DOF of the holographic MIMO (HMIMO) channel and give a upper bound of the DOF with strong mutual coupling. Our numerical simulations demonstrate that a dense array can support more DOF per unit aperture as compared to a half-wavelength MIMO system.

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Investigation and Comparison of 5G Channel Models: From Qua DRi Ga, NYUSIM,and MG5G Perspectives

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Chinese Journal of Electronics 2022年第1期31卷 1-17页

作者： PANG Lihua ZHANG Jin ZHANG Yang HUANG Xinyi chen yijian LI Jiandong School of Communication and Information Engineering Xi'an University of Science and Technology State Key Laboratory of Integrated Service Networks Xidian University National Mobile Communications Research Laboratory Southeast University Algorithm Department ZTE Corporation

This paper investigates and compares three channel models for the fifth generation(5 G) wireless communications: the quasi deterministic radio channel generator(Qua DRi Ga), the NYUSIM channel simulator model developed by New York University, and the more general 5 G(MG5 G) channel model. First, the characteristics of the modeling processes of the three models are introduced from the perspective of model framework.Then, the small-scale parameter modeling strategies of the three models are compared from space/time/frequency domains as well as polarization aspect. In particular, the drifting of small-scale parameters is introduced in detail.Finally, through the simulation results of angular power spectrum, Doppler power spectrum density, temporal autocorrelation function, power delay profile, frequency correlation function, channel capacity, and eigenvalue distribution, the three models are comprehensively investigated. According to the simulation results, we clearly analyze the impact of the modeling strategy on the three channel models and give certain evaluations and suggestion which lay a solid foundation for link and system-level simulations for 5 G transmission algorithms.

关键词： 5G Channel model Small-scale parameter Modeling strategy Channel simulation

An intelligent identification method of safety risk while drilling in gas drilling

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Petroleum Exploration and Development 2022年第2期49卷 428-437页

作者： HU Wanjun XIA Wenhe LI Yongjie JIANG Jun LI Gao chen yijian School of Electrical Engineering and Information Southwest Petroleum UniversityChengdu 610500China State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Chengdu 610500China School of Oil&Gas Engineering Southwest Petroleum UniversityChengdu 610500China School of Computer Science Southwest Petroleum UniversityChengdu 610500China

In view of the shortcomings of current intelligent drilling technology in drilling condition representation, sample collection, data processing and feature extraction, an intelligent identification method of safety risk while drilling was established. The correlation analysis method was used to determine correlation parameters indicating gas drilling safety risk. By collecting monitoring data in the safety risk period of more than 20 wells, a sample database of a variety of safety risks in gas drilling was established, and the number of samples was expanded by using the method of few-shot learning. According to the forms of gas drilling monitoring data samples, a two-layer convolution neural network architecture was designed, and multiple convolution cores of different sizes and weights were set to realize the vertical and horizontal convolution computations of samples to extract and learn the variation law and correlation characteristics of multiple monitoring parameters. Finally, based on the training results of neural network, samples of different kinds of safety risks were selected to enhance the recognition accuracy. Compared with the traditional BP(error back propagation) full-connected neural network architecture, this method can more deeply and effectively identify safety risk characteristics in gas drilling, and thus identify and predict risks in advance, which is conducive to avoid and quickly solve safety risks while drilling. Field application has proved that this method has an identification accuracy of various safety risks while drilling in the process of gas drilling of about 90% and is practical.

关键词： gas drilling safety risk intelligent risk identification few-shot learning convolution neural network measurement while drilling

介质微球光场调控制备多级银微纳结构及其表面增强拉曼光谱研究(特邀)

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中国激光 2024年第4期51卷 266-277页

作者：陈冰冰闫胤洲赵晨赵艳蒋毅坚北京工业大学材料与制造学部激光工程研究院北京100124

表面增强拉曼光谱(SERS)是一种高灵敏的分子振动指纹光谱技术。光辅助化学还原制备SERS衬底具有成本低、环境适用性强等优势,但在微纳结构多样化制造方面存在局限性,限制了SERS衬底的检出性能。笔者系统研究了介质微球独特的聚焦特性,... 详细信息

表面增强拉曼光谱(SERS)是一种高灵敏的分子振动指纹光谱技术。光辅助化学还原制备SERS衬底具有成本低、环境适用性强等优势,但在微纳结构多样化制造方面存在局限性,限制了SERS衬底的检出性能。笔者系统研究了介质微球独特的聚焦特性,揭示了微球直径对聚焦光场分布的调控规律,在微球底部实现了可控的光场空间分布,实现了多级银微纳结构的快速光还原合成。进一步,通过优化制备参数(前驱液浓度比、激光辐照功率及辐照时间),成功制备了具有优异拉曼增强效果的多级银纳米颗粒/银微环/介质微球(AgNPs/AgMRs/MS)复合结构。通过介质微球和多级银微纳结构(AgNPs/AgMRs)中的光场耦合,即微球聚焦、多级银微纳结构局域表面等离激元共振以及复合结构定向发射等,实现了10^(-14)mol/L的痕量检测,增强因子可达9.50×10^(9),为光化学还原制备高性能介质-金属复合SERS衬底提供了新思路。

关键词：光谱学表面增强拉曼光谱多级银微纳结构光化学还原介质微球

Atomically Dispersed Ruthenium Catalysts with Open Hollow Structure for Lithium-Oxygen Batteries

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Nano-Micro Letters 2024年第2期16卷 154-164页

作者： Xin chen Yu Zhang Chang chen Huinan Li Yuran Lin Ke Yu Caiyun Nan chen chen Beijing Advanced Innovation Center for Materials Genome Engineering Institute of Solid State ChemistryUniversity of Science and Technology BeijingBeijing 100083People’s Republic of China Engineering Research Center of Advanced Rare Earth Materials Department of ChemistryTsinghua UniversityBeijing 100084People’s Republic of China Beijing Key Laboratory of Energy Conversion and Storage Materials Institution College of ChemistryBeijing Normal UniversityBeijing 100875People’s Republic of China

Lithium–oxygen battery with ultrahigh theoretical energy density is considered a highly competitive next-generation energy storage device,but its practical application is severely hindered by issues such as difficult decomposition of discharge products at present.Here,we have developed N-doped carbon anchored atomically dispersed Ru sites cathode catalyst with open hollow structure(h-RuNC)for Lithium–oxygen battery.On one hand,the abundance of atomically dispersed Ru sites can effectively catalyze the formation and decomposition of discharge products,thereby greatly enhancing the redox kinetics.On the other hand,the open hollow structure not only enhances the mass activity of atomically dispersed Ru sites but also improves the diffusion efficiency of catalytic molecules.Therefore,the excellent activity from atomically dispersed Ru sites and the enhanced diffusion from open hollow structure respectively improve the redox kinetics and cycling stability,ultimately achieving a high-performance lithium–oxygen battery.

关键词： Atomically dispersed Open hollow structure Discharge product Lithium Oxygen battery

RIS:Spatial-Wideband Effect Analysis and Off-Grid Channel Estimation

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ZTE Communications 2022年第1期20卷 57-62页

作者： JIAN Mengnan ZHANG Nan chen yijian State Key Laboratory of Mobile Network and Mobile Multimedia Technology Shenzhen 518055China Algorithm Department Wireless Product R&D InstituteZTE Corpo-rationShenzhen 518057China

As a critical candidate technology for 5G-advanced and 6G,reconfigurable intelligent surfaces(RIS)have received extensive atten-tion from academia and industry.RIS has the promising features of passiveness,reconfigurable ability,and low cost.RIS channel estimation faces the challenges of high matrix dimension,passive estimation,and spatial-wideband effect.In this article,we analyze the impact of the spatial-wideband effect on the RIS channel to account for the propagation delay across RIS elements and estimate sparse channel parameters such as angle and gain through a super-resolution compressive sensing(CS)algorithm.The simulation results explore the influence of the spatial-wideband effect on the RIS channel and verify the effectiveness of the proposed algorithm.

关键词： RIS channel estimation spatial-wideband effect compressed sensing

Advances in the application of hydrogel-based scaffolds for tendon repair

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Genes & Diseases 2024年第4期11卷 296-313页

作者： Renqiang chen Fanglin chen Kenian chen Jian Xu Department of Orthopedics The First Affiliated HospitalZhejiang University School of MedicineHangzhouZhejiang 310003China Department of Orthopedics The Fourth Affiliated Hospital of Guangxi Medical UniversityLiuzhou Guangxi 545005China

Tendon injuries often lead to joint dysfunction due to the limited self-regeneration capacity of tendons.Repairing tendons is a major challenge for surgeons and imposes a signif-icant financial burden on society.Therefore,there is an urgent need to develop effective stra-tegies for repairing injured tendons.Tendon tissue engineering using hydrogels has emerged as a promising approach that has attracted considerable interest.Hydrogels possess excellent biocompatibility and biodegradability,enabling them to create an extracellular matrix-like growth environment for cells.They can also serve as a carrier for cells or other substances to accelerate tendon repair.In the past decade,numerous studies have made significant prog-ress in the preparation of hydrogel scaffolds for tendon healing.This review aims to provide an overview of recent research on the materials of hydrogel-based scaffolds used for tendon tis-sue engineering and discusses the delivery systems based on them.

关键词： Application Hydrogel-based Repairscaffolds Review Tendon injury Tissue engineering