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Joint task scheduling and multi-UAV deployment for aerial computing in emergency communication networks

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Science China(Information Sciences) 2023年第9期66卷 239-258页

作者： Tiankui ZHANG Chaobin CHEN Yu xu Jonathan LOO wenjun xu School of Information and Communication Engineering Beijing University of Posts and Telecommunications School of Computing and Engineering University of West London School of Artificial Intelligence Beijing University of Posts and Telecommunications

This article studies mobile edge computing technologies enabled by unmanned aerial vehicles(UAVs) in disasters. First, considering that the ground servers may be damaged in emergency scenarios, we proposed an air-ground cooperation architecture based on ad-hoc UAV networks. We defined the system cost as the weighted sum of task delay and energy consumption because of different delay sensitivity and energy sensitivity tasks in emergency communication networks. Then, we formulated the system cost-minimization problem of task scheduling and multi-UAV deployments. To solve the proposed mixed integer nonlinear programming problem, we decomposed it to two sub-problems that were solved by proposing a swap matchingbased task scheduling sub-algorithm and a successive convex approximation-based multi-UAV deployment sub-algorithm. Accordingly, we propose a joint optimization algorithm by iterating the two sub-algorithms to obtain a low complexity sub-optimal solution. Finally, the simulation results show that(i) the proposed algorithm converges in several iterations, and(ii) compared with the benchmark algorithms, the proposed algorithm has better performance of reducing task delay and energy consumption and achieves a good tradeoff between them for diverse tasks.

关键词： emergency communication mobile edge computing swap matching algorithm unmanned aerial vehicle

Graph Laplacian Matrix Learning from Smooth Time-Vertex Signal

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China Communications 2021年第3期18卷 187-204页

作者： Ran Li Junyi Wang wenjun xu Jiming Lin Hongbing Qiu School of Telecommunications Engineering Xidian UniversityXi’an 710071ShanxiChina Key Laboratory of Cognitive Radio and Information Processing Ministry of Education(Guilin University of Electronic Technology)Guilin 541004GuangxiChina School of Information and Communication Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China

In this paper,we focus on inferring graph Laplacian matrix from the spatiotemporal signal which is defined as“time-vertex signal”.To realize this,we first represent the signals on a joint graph which is the Cartesian product graph of the time-and *** assuming the signals follow a Gaussian prior distribution on the joint graph,a meaningful representation that promotes the smoothness property of the joint graph signal is ***,by decoupling the joint graph,the graph learning framework is formulated as a joint optimization problem which includes signal denoising,timeand vertex-graphs learning ***,two algorithms are proposed to solve the optimization problem,where the discrete second-order difference operator with reversed sign(DSODO)in the time domain is used as the time-graph Laplacian operator to recover the signal and infer a vertex-graph in the first algorithm,and the time-graph,as well as the vertex-graph,is estimated by the other *** on both synthetic and real-world datasets demonstrate that the proposed algorithms can effectively infer meaningful time-and vertex-graphs from noisy and incomplete data.

关键词： Cartesian product graph discrete secondorder difference operator Gaussian prior distribution graph Laplacian matrix learning spatiotemporal smoothness time-vertex signal

Spectrum Efficiency Maximization for Cooperative Power Beacon-Enabled Wireless Powered Communication Networks

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China Communications 2021年第12期18卷 230-251页

作者： wenjun xu Wei Chen Yongjian Fan Zhi Zhang Xinxin Shi Key Lab of Universal Wireless Communications Ministry of EducationBeijing University of Posts and TelecommunicationsBeijing 100876China Hebei Key Laboratory of Security and Protection Information Sensing and Processing Hebei University of EngineeringHandan 056038China State Key Laboratory of Networking and Switching Technology Beijing University of Posts and TelecommunicationsBeijing 100876China Beijing Telecom Planning&Designing Institute Co. Ltd.Beijing 100048China

We consider a spectrum efficiency(SE)maximization problem for cooperative power beacon-enabled wireless powered communication networks(CPB-WPCNs),where each transmitter harvests en-ergy from multi-antenna power beacons(PBs)and transmits data to the corresponding *** data transmission,both orthogonal transmission,i.e.,the time splitting(TS)mode,and non-orthogonal trans-mission,i.e.,the interference channel(IC)mode,are *** to improve the system SE,the energy beamformers of PBs,the transmit power,and the transmit time duration of transmitters are jointly *** the TS mode,the original non-convex problem is transformed into a convex opti-mization problem by means of variable substitution and semidefinite relaxation(SDR).The rank-one na-ture of this SDR is proved,and then a Lagrange-dual based fast algorithm is proposed to obtain the opti-mal solution with much lower *** the IC mode,to conquer the strong non-convexity of the problem,a branch-reduce-and-bound(BRB)mono-tonic optimization algorithm is designed as a ***,a low-complexity distributed suc-cessive convex approximation(SCA)algorithm is ***,simulation results validate the perfor-mance of the proposed algorithms,achieving optimal-ity within only 1%∼2%computation time compared to the CVX solver in the TS mode and achieving 98%of the optimal performance in the IC mode.

关键词： spectrum efficiency power beacon WPCN time splitting interference channel wireless power transfer

A policy gradient algorithm integrating long and short-term rewards for soft continuum arm control

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Science China(Technological Sciences) 2022年第10期65卷 2409-2419页

作者： DONG Xiang ZHANG Jing CHENG Long xu wenjun SU Hang MEI Tao School of Electrical Engineering and Automation Anhui UniversityHefei 230601China State Key Laboratory for Control and Management of Complex Systems Institute of AutomationChinese Academy of SciencesBeijing 100190China Robotics Research Center Peng Cheng LaboratoryShenzhen 518055China

The soft continuum arm has extensive application in industrial production and human life due to its superior safety and flexibility. Reinforcement learning is a powerful technique for solving soft arm continuous control problems, which can learn an effective control policy with an unknown system model. However, it is often affected by the high sample complexity and requires huge amounts of data to train, which limits its effectiveness in soft arm control. An improved policy gradient method, policy gradient integrating long and short-term rewards denoted as PGLS, is proposed in this paper to overcome this issue. The shortterm rewards provide more dynamic-aware exploration directions for policy learning and improve the exploration efficiency of the algorithm. PGLS can be integrated into current policy gradient algorithms, such as deep deterministic policy gradient(DDPG). The overall control framework is realized and demonstrated in a dynamics simulation environment. Simulation results show that this approach can effectively control the soft arm to reach and track the targets. Compared with DDPG and other model-free reinforcement learning algorithms, the proposed PGLS algorithm has a great improvement in convergence speed and performance. In addition, a fluid-driven soft manipulator is designed and fabricated in this paper, which can verify the proposed PGLS algorithm in real experiments in the future.

关键词： soft arm control Cosserat rod deep reinforcement learning policy gradient algorithm high sample complexity

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Semantic information processing in industrial networks

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The Journal of China Universities of Posts and Telecommunications 2022年第1期29卷 41-49页

作者： Yao Shengshi Wang Sixian Dai Jincheng Niu Kai xu wenjun Zhang Ping The Key Laboratory of Universal Wireless Communications(Ministry of Education) Beijing University of Posts and TelecommunicationsBeijing 100876China The Peng Cheng Laboratory Nanshan DistrictShenzhen 518052China The State Key Laboratory of Networking and Switching Technology Beijing University of Posts and TelecommunicationsBeijing 100876China

The industrial Internet of things(industrial IoT, IIoT) aims at connecting everything, which poses severe challenges to existing wireless communication. To handle the demand for massive access in future industrial networks, semantic information processing is integrated into communication systems so as to improve the effectiveness and efficiency of data transmission. The semantic paradigm is particularly suitable for the purpose-oriented information exchanging scheme in industrial networks. To illustrate its applicability, typical industrial data are investigated, i.e., time series and images. Simulation results demonstrate the superiority of semantic information processing, which achieves a better rate-utility tradeoff than conventional signal processing.

关键词： semantic information semantic communication industrial Internet of things signal processing

Photovoltaic Power Generation Power Prediction under Major Extreme Weather Based on VMD-KELM

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Energy Engineering 2024年第12期121卷 3711-3733页

作者： Yuxuan Zhao Bo Wang Shu Wang wenjun xu Gang Ma National Key Laboratory of Renewable Energy Grid Integration China Electric Power Research InstituteBeijing100192China School of Electrical and Automation Engineering Nanjing Normal UniversityNanjing210023China

The output of photovoltaic power stations is significantly affected by environmental factors,leading to intermittent and fluctuating power *** the increasing frequency of extreme weather events due to global warming,photovoltaic power stations may experience drastic reductions in power generation or even complete shutdowns during such *** integration of these stations on a large scale into the power grid could potentially pose challenges to *** address this issue,in this study,we propose a network architecture based on VMDKELMfor predicting the power output of photovoltaic power plants during severe weather ***,a grey relational analysis is conducted to identify key environmental factors influencing photovoltaic power ***,GMM clustering is utilized to classify meteorological data points based on their probabilities within different Gaussian distributions,enabling comprehensive meteorological clustering and extraction of significant extreme weather *** data are decomposed using VMD to Fourier transform,followed by smoothing processing and signal reconstruction using KELM to forecast photovoltaic power output under major extreme weather *** proposed prediction scheme is validated by establishing three prediction models,and the predicted photovoltaic output under four major extreme weather conditions is analyzed to assess the impact of severe weather on photovoltaic power station *** experimental results show that the photovoltaic power output under conditions of dust storms,thunderstorms,solid hail precipitation,and snowstorms is reduced by 68.84%,42.70%,61.86%,and 49.92%,respectively,compared to that under clear day *** photovoltaic power prediction accuracies,in descending order,are dust storms,solid hail precipitation,thunderstorms,and snowstorms.

关键词： Major extreme weather photovoltaic power prediction weather clustering VMD-KELM network prediction model

Horizontal crustal movement before the great Wenchuan earthquake obtained from GPS observations in the regional network

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Earthquake Science 2009年第5期22卷 471-478页

作者： Guohua Gu Wuxing Wang Yueren xu wenjun Li Institute of Earthquake Science China Earthquake Administration Beijing 100036 China

The great Wenchuan earthquake of M8.0 on May 12, 2008, occurred in an area with dense GPS observation stations in the regional network of the Crustal Movement Observation Network of China （CMONOC）. Non-continuous observations were carried out at the 1 000 GPS stations of the regional network in 1999, 2001, 2004 and 2007. The horizontal displacements at GPS stations in the regional network before the Wenchuan earthquake show that the main driving tectonic force of the earthquake was the northward pushing of the Indian plate, added at the same time by the pushing of plates on the east and south. In comparison to the displacements in other regions, the horizontal displacements near and around the seismic area is characterized by diverging eastward displacements, that is, the stations to the north of the epicenter moved in the ENE direction while those to the south of epicenter moved in ESE direction with smaller displacements at stations near the epicenter. The accuracy of the estimated strain results is briefly discussed. In order to obtain the anomalous information before the earthquake, the methods of both best fits by trend surface and statistics have been used in the study for finding the future epicentral area from the strain accumulations in the regional network observed from 1999 to 2007 before the Wenchuan earthquake. Besides the epicentral area of the western Kunlun mountain pass earthquake of M8.1 in 2001, the results of best fits by trend surfaces of the strain accumulations from 1999 to 2007 in the regional network show that the Wenchuan earthquake occurred at the eastern fringe of a large area with relatively large accumulations of the first shear strains and also at the northeastern fringe of a smaller area with significant accumulated areal compressions. The statistics of the accumulations of the strain components demonstrates that they also showed anomalous distribution pattems in this area and its neighborhood with increasing accumulations of both she

关键词： Wenchuan earthquake horizontal crustal movement strain accumulation GPS earthquake prediction

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

Prediction of the thermal conductivity of Mg–Al–La alloys by CALPHAD method

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International Journal of Minerals,Metallurgy and Materials 2024年第1期31卷 129-137页

作者： Hongxia Li wenjun xu Yufei Zhang Shenglan Yang Lijun Zhang Bin Liu Qun Luo Qian Li State Key Laboratory of Advanced Special Steels&Shanghai Key Laboratory of Advanced Ferrometallurgy&School of Materials Science and Engineering Shanghai UniversityShanghai 200444China National Engineering Research Center for Magnesium Alloys Chongqing UniversityChongqing 400044China State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China College of Materials Science and Engineering Chongqing UniversityChongqing 400044China National Key Laboratory of Advanced Casting Technologies Chongqing UniversityChongqing 400044China

Mg-Al alloys have excellent strength and ductility but relatively low thermal conductivity due to Al *** accurate prediction of thermal conductivity is a prerequisite for designing Mg-Al alloys with high thermal ***,databases for predicting temperature-and composition-dependent thermal conductivities must be *** this study,Mg-Al-La alloys with different contents of Al2La,Al3La,and Al11La3phases and solid solubility of Al in the α-Mg phase were *** influence of the second phase(s) and Al solid solubility on thermal conductivity was *** results revealed a second phase transformation from Al_(2)La to Al_(3)La and further to Al_(11)La_(3)with the increasing Al content at a constant La *** degree of the negative effect of the second phase(s) on thermal diffusivity followed the sequence of Al2La>Al3La>Al_(11)La_(3).Compared with the second phase,an increase in the solid solubility of Al in α-Mg remarkably reduced the thermal *** the basis of the experimental data,a database of the reciprocal thermal diffusivity of the Mg-Al-La system was established by calculation of the phase diagram (CALPHAD)*** a standard error of±1.2 W/(m·K),the predicted results were in good agreement with the experimental *** established database can be used to design Mg-Al alloys with high thermal conductivity and provide valuable guidance for expanding their application prospects.

关键词： magnesium alloy thermal conductivity thermodynamic calculations materials computation