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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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DOA estimation via sparse recovering from the smoothed covariance vector

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Journal of Systems Engineering and electronics 2016年第3期27卷 555-561页

作者： Jingjing Cai Dan Bao Peng Li school of electronics Engineering Xidian University

A direction of arrival（DOA） estimation algorithm is proposed using the concept of sparse representation. In particular, a new sparse signal representation model called the smoothed covariance vector（SCV） is established, which is constructed using the lower left diagonals of the covariance matrix. DOA estimation is then achieved from the SCV by sparse recovering, where two distinguished error limit estimation methods of the constrained optimization are proposed to make the algorithms more robust. The algorithm shows robust performance on DOA estimation in a uniform array, especially for coherent signals. Furthermore, it significantly reduces the computational load compared with those algorithms based on multiple measurement vectors（MMVs）. Simulation results validate the effectiveness and efficiency of the proposed algorithm.

关键词： array signal processing convex optimization direction of arrival(DOA) estimation sparse representation

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Quantum correlations generation and distribution in a universal covariant quantum cloning circuit

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Science China(Information Sciences) 2017年第12期60卷 248-255页

作者： Xijun REN school of Physics and electronics Henan University

We discussed the distribution and generation of quantum correlations in a universal covariant quantum cloning circuit. Specifically, we first considered the distribution of quantum correlation, i.e., quantum discord, among the four qubits of the circuit. Then, we analyzed the generation of genuine 3-or 4-qubit entanglement in the cloning process. It is found that the circuit generates genuine 4-qubit GHZ(GreenbergerHorne-Zeilinger)-type state while only W-type 3-qubit state could be generated. These results illustrate the special quantum correlation manipulation capabilities of the cloning circuit.

关键词： quantum information quantum correlation quantum discord universal covariant quantum cloning circuit genuine multipartite quantum correlation

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Studying the intermittent stable theorem and the synchronization of a delayed fractional nonlinear system

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Chinese Physics B 2013年第8期22卷 339-345页

作者：胡建兵赵灵冬谢正光 school of electronics & Information Nantong University

In this paper, an intermittent synchronizing delayed fractional nonlinear system is studied. We propose a novel intermittent stable theorem for the delayed fractional system and derive a new synchronization criterion for delayed fractional systems by means of fractional stable theorem and the differential inequality method. Intermittent synchronizing fractional delayed Newton-Leipnik system is taken as an illustrative example and numerical simulation of this example is presented to show the feasibility and effectiveness of the proposed theorem.

关键词： fractional delay stability intermittent synchronization

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Improved Beam Steering Method Using OAM Waves

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Computer Systems Science & Engineering 2023年第7期46卷 417-431页

作者： Nidal Qasem Ahmad Alamayreh Department of electronics and communications Engineering Al-Ahliyya Amman UniversityAmmanJordan

Orbital Angular Momentum(OAM)is an intrinsic feature of electromagnetic waves which has recently found many applications in several areas in radio and *** this paper,we use OAM wave characteristics to present a simple method for beam steering over both elevation and azimuth *** design overcomes some limitations of traditional steering methods,such as limited dynamic range of steering,the design complexity,bulky size of the steering structure,the limited bandwidth of operation,and low *** on OAM wave characteristics,the proposed steering method avoids design complexities by adopting a simple method for generating the OAM-carrying *** waves are generated by an array of Planar Circular Dipole(PCD)*** elements are designed to cover a wide bandwidth range between 3 and 30 *** transmitting array shows an enhanced gain value from 8.5 dBi to almost 11.5 dBi at the broadside *** the enhanced PCD-based OAM generation,the novelty of the design lies in a new method of beam *** steering is then performed by controlling the electrical feeding of the PCD elements;the beam azimuthal location is managed by turning off some of the PCD elements,while the elevation is determined by changing the gradient phase of excitation for the turned-on PCD *** analysis of the steering method is carried out by finding the mathematical model of the system and the generated *** performance has been verified through numerical simulators.

关键词： Antenna array bandwidth beam steering orbital angular momentum

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A cost-efficient quantum access network with qubit-based synchronization

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Science China(Physics,Mechanics & Astronomy) 2024年第4期67卷 12-22页

作者： Chunfeng Huang Ye Chen Tingting Luo Wenjie He Xin Liu Zhenrong Zhang Kejin Wei Guangxi Key Laboratory for Relativistic Astrophysics School of Physical Science and TechnologyGuangxi UniversityNanning 530004China Guangxi Key Laboratory of Multimedia communications and Network Technology School of Computer Electronics and InformationGuangxi UniversityNanning 530004China

Quantum key distribution(QKD)is a physical layer encryption technique that enables two distant parties to exchange secure keys with information-theoretic *** the last two decades,QKD has transitioned from laboratory research to real-world applications,including multi-user quantum access networks(QANs).This network structure allows users to share a single-photon detector at a network node through time-division multiplexing,thereby significantly reducing the network ***,current QAN implementations require additional hardware for auxiliary tasks such as time *** address this issue,we propose a cost-efficient QAN that uses qubit-based *** this approach,the transmitted qubits facilitate time synchronization,eliminating the need for additional synchronization *** tested our scheme by implementing a network for two users and successfully achieved average secure key rates of 53.84 kbps and 71.90 kbps for each user over a 50-km commercial fiber *** addition,we investigated the capacity of the access network under cross-talk and loss *** simulation results demonstrate that this scheme can support a QAN with 64 users with key rates up to 1070 *** work provides a feasible and cost-effective way to implement a multi-user QKD network,further promoting the widespread application of QKD.

关键词： quantum key distribution quantum access network qubit-based synchronization

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Low-Complexity LS Algorithm Using Coordinate Transformation

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Chinese Journal of electronics 2017年第1期26卷 156-159页

作者： YAN Wen XIE Yizhuang ZHU Bocheng CHEN He MA Cuimei school of Information and electronics Beijing Institute of Technology school of electronics Engineering and Computer Science Peking University

To reduce the computational complexity, decrease hardware resource consumption, and make it practicable, we propose a novel coordinate transformation based low-complexity Least squares(LS) algorithm. The positive integral variable is set as a reference coordinate and coefficients are transformed to be constant. The fitting polynomial in the reference coordinate system can be easily realized with lower complexity. To achieve the fitting curve in the original coordinate system, coordinate transformation is needed. Compared with the conventional LS fitting, our implementation results show that the proposed LS fitting algorithm can greatly reduce hardware resources in the premise of meeting the precision requirements.

关键词： Least squares(LS) fitting Reference coordinate Coordinate transformation Low computational complexity

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Fiber-based quantum secure direct communication without active polarization compensation

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Science China(Physics,Mechanics & Astronomy) 2022年第12期65卷 91-96页

作者： Xin Liu Di Luo Guangshen Lin Zihao Chen Chunfeng Huang Shizhuo Li Chengxian Zhang Zhenrong Zhang Kejin Wei Guangxi Key Laboratory for Relativistic Astrophysics School of Physical Science and TechnologyGuangxi UniversityNanning530004China Guangxi Key Laboratory of Multimedia communications and Network Technology School of ComputerElectronicsand InformationGuangxi UniversityNanning530004China

Quantum secure direct communication(QSDC)that allows people to directly transmit confidential information through insecure channels is an important branch of quantum *** widespread adoption of the QSDC demands the development of simple and stable ***,most of the existent QSDC systems involve a complex self-alignment process at the initial stage and additional hardware to compensate environmental *** this study,we present a fiber-based QSDC system without active polarization *** system comprises a stable transmitter and a novel Sagnac-Mach-Zehnder interferometer for security *** robust system simplifies the self-alignment and is immune to environmental *** robustness of the system was theoretically and experimentally verified,and low bit error rates in a 12 min continuous operation with an active polarization scrambler were *** addition,we performed a proof-of-principle QSDC demonstration,and a secrecy capacity of 3.43 kbps over a 5 km fiber with a detection bit error rate of 0.85%±0.07%and a quantum bit error rate of 0.42%±0.05%were *** results confirm the viability of the proposed QSDC system for practical applications.

关键词： quantum secure direct communication Sagnac-Mach-Zehnder interferometer without active polarization compensation

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Cooperative NOMA Based on OAM Transmission for Beyond 5G Applications

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Computer Systems Science & Engineering 2023年第5期45卷 1187-1197页

作者： Mohammad Alkhawatrah electronics and communications Engineering Department Al-Ahliyya Amman UniversityAmmanJordan

Cooperative non-orthogonal multiple access(NOMA)is heavily studied in the literature as a solution for 5G and beyond 5G *** NOMA transmits a superimposed version of all users’messages simultaneously with the aid of a relay,after that,each user decodes its own ***,NOMA is deemed as a spectral efficient *** emerging technique exploits orbital angular momentum(OAM),where OAM is an attractive character of electromagnetic *** gathered a great deal of attention in recent years(similar to the case with NOMA)due to its ability to enhance electromagnetic spectrum exploitation,hence increasing the achieved transmission ***,OAM-based transmission suffers from wave divergence,especially at high OAM *** OAM limitation reduces the transmission *** distance can be extended via cooperative relays(part of cooperative NOMA).Relay helps the source to transmit packets to the destination by providing an additional connection to handle the transmission and provide a shorter distance between source and *** this paper,we propose employing OAM transmission in the cooperative NOMA *** experiments show that OAM transmission helps cooperative NOMA in achieving higher throughput compared to the conventional cooperative ***,the cooperation part of cooperative NOMA eases the divergence problem of *** addition,the proposed system outperforms the standalone cooperative OAM-based solution.

关键词： 5G cooperative network NOMA OAM relay throughput

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Study on optimal state estimation strategy with dual distributed controllers based on Kalman filtering

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High Technology Letters 2019年第1期25卷 105-110页

作者： Chen Yawen Wang Zhuwei Fang Chao Xu Guangshu Zhang Yanhua school of Information and communications Engineering Beijing University of Technology

Considering dual distributed controllers, a design of optimal state estimation strategy is studied for the wireless sensor and actuator network(WSAN). In particular, the optimal linear quadratic(LQ) control strategy with estimated plant state is formulated as a non-cooperative game with network-induced delays. Then, using the Kalman filter approach, an optimal estimation of the plant state is obtained based on the information fusion of the distributed controllers. Finally, an optimal state estimation strategy is derived as a linear function of the current estimated plant state and the last control strategy of multiple controllers. The effectiveness of the proposed closed-loop control strategy is verified by the simulation experiments.

关键词： optimal state estimation strategy wireless sensor and actuator network(WSAN) distributed controllers Kalman filter network-induced delays

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