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arXiv 2018年

作者： Lan, Chuwen Wu, Hailian Yang, Daquan Gao, Zehua Beijing Laboratory of Advanced Information Networks Beijing Key Laboratory of Network System Architecture and Convergence Acknowledgment School of Information and Communication Engineering Beijing University of Posts and Telecommunications Beijing100876 China

All-dielectric metamaterials composed of high index and low loss dielectric resonators have become a promising way for high-efficient optical devices. However, fabricating terahertz all-dielectric metamaterials and actively tuning their properties still remain challenges. In this paper, an effective method has been developed to prepare high-quality microspheres based all-dielectric metamaterial operating in terahertz (THz) range. Then, we propose a magnetically tunable THz all-dielectric metamaterial based on liquid crystal (LC). The all-dielectric metamaterial is immersed into LC and tuned by external magnetic field. We show that the induced Mie resonances can be effectively tuned by external magnetic field and the tunability is highly sensitive to the directors of applied magnetic field. A good tunability performance is obtained for the first electric resonance. This work provides a new method for high-quality THz all-dielectric metamaterials and paves a promising way for tunable THz all-dielectric metamaterial, which would find considerable applications in THz devices. Copyright © 2018, The Authors. All rights reserved.

关键词： Metamaterials

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An improved and more accurate expression for a PDF related to eigenvalue-based spectrum sensing

arXiv

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arXiv 2018年

作者： Zhou, Fuhui Beaulieu, Norman C. School of Information Engineering Nanchang University 330031 China Beijing University of of Posts and Telecommunications Beijing Key Laboratory of Network System Architecture and Convergence Beijing100876 China

Cooperative spectrum sensing based on the limiting eigenvalue ratio of the covariance matrix offers superior detection performance and overcomes the noise uncertainty problem. While an exact expression exists, it is complex and multiple useful approximate expressions have been published in the literature. An improved, more accurate, integral solution for the probability density function of the ratio is derived using order statistical analysis to remove the simplifying, but incorrect, independence assumption. Thereby, the letter makes an advance in the rigorous theory of eigenvalue-based spectrum sensing. Copyright © 2018, The Authors. All rights reserved.

关键词： Eigenvalues and eigenfunctions

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Research on Measurement Uncertainty of Absorption Cross Section in a Reverberation Chamber

Research on Measurement Uncertainty of Absorption Cross Sect...

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Conference on Precision Electromagnetic Measurements

作者： Jienan Liu Ke Liu Xin Bian Shufang Li Division of Electronics and Information Technology National Institute of Metrology Beijing China Beijing Key Laboratory of Network System Architecture and Convergence Beijing University of Posts and Telecommunications Beijing China

The absorption cross section (ACS) of absorbers are measured in a reverberation chamber and the relative uncertainty of measurements is calculated. The ACS is calculated by a time-domain method at frequencies in the range 1-3GHz. The average relative uncertainty of the ACS over the frequency range is 0.02 by the measurements in eight different configurations of absorbers and antennas, which shows good experimental stability.

关键词： Absorbers Absorption Cross Section Measurement Uncertainty Reverberation Chamber Time-domain Method

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The Directional Radiation Metamaterial Lens Based on Quasi-conformal Transformation Method

The Directional Radiation Metamaterial Lens Based on Quasi-c...

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2018 International Conference on Energy, Power and Materials Engineering (EPME 2018)

作者： Chao GAO Xiao-kang WU Xiao-hua HUANG Chong XU Bin WEI Li DENG Energy Storage and Electrotechnics Department China Electric Power Research Institute Beijing Key Laboratory of Network System Architecture and Convergence Beijing University of Posts and Telecommunications

In this paper, a practical directional radiation metamaterial lens using quasi-conformal transformation(QCTC) method is proposed. The design of arched metamaterial lens can be widely put on any conformal antenna shaped in arc or cylinder, and behaves similarly to a linear array antenna. In the proceeding of designing, QCTC method is employed to minimize values of permittivity and permeability in lens' s transform medium. Moreover, this method overcomes the shortcomings of singular values and computational complexity compared to traditional transformation optics. The lens made of quasi-isotropic material can perfectly balance realization and performance. Besides, the constitutive parameters are computed using Laplace equations with Robin boundary condition instead of traditional Dirichlet and Neumann conditions. Through compared simulation results in different situations using COMSOL Multiphysics, verifying the correctness of lens designed.

关键词： Radiation enhancing metamaterial lens Quasi-conformal transformation optics(QCTC) Transform medium Quasi-isotropic material

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Improving throughput through dynamically tuning contention window size in dense wireless network

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The Journal of China Universities of Posts and Telecommunications 2017年第4期24卷 27-33页

作者： Lin Shangjuan Wen Xiangming Hu Zhiqun Lu Zhaoming School of Information and Communication Engineering Beijing University of Posts and Telecommunications Beijing 100876 China Beijing Key Laboratory of Network System Architecture and Convergence Beijing University of Posts and Telecommunications Beijing 100876 China Beijing Laboratory of Advanced Information Networks Beijing University of Posts and Telecommunications Beijing 100876 China

With the boom of wireless devices, the number of wireless users under wireless local area networks （WLANs） has increased dramatically. However, the standard baekoff mechanism in IEEE 802.11 adopts fixed initial contention window （CW） size without considering changes of network load, which leads to a high collision probability and low channel utilization in bursty arrivals. In this paper, a novel CW dynamic adjustment scheme is proposed to achieve high throughput performance in dense user environment. In the proposed scheme, the initial CW size is dynamically adjusted to optimum according to the measured packet collision probability. Simulation results show that the proposed scheme can significantly improve the throughput performance.

关键词： wireless local area network （WLAN） dense user environment contention window （CW） dynamic optimization

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Anti-blockage Beam Training for Massive MIMO Millimeter Wave systems

Anti-blockage Beam Training for Massive MIMO Millimeter Wave...

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IEEE Vehicular Technology Conference

作者： Zhaoqiang Li Danpu Liu Xiaoyong Wu Feng Yu Beijing Laboratory of Advanced Information Network Beijing Key Laboratory of Network System Architecture and Convergence Beijing University of Posts and Telecommunications Beijing P.R. China Huawei Technologies Co. Ltd Beijing P.R. China

Due to the short wavelength of millimeter wave (mmWave) and high directional beamforming, the 60GHz massive MIMO systems are highly vulnerable to link blockage. Beam switching to unblocked direction is an effective solution to overcome blockage. To this end, a set of backup beam pairs for beam switching must be identified at initial beam training. In this work, a low complexity beam training scheme with support for backup beam identification is proposed. Considering sparsity and clustered characteristics of mmWave channels and high probability for adjacent beams to be simultaneously blocked, we propose a new criterion for the selection of backup beams based on peak beam grouping, and design two beam grouping algorithms. The detailed procedure for beam switching when a blockage occurs is also given. Simulation results show that the proposed beam training scheme achieves near-optimal performance at initial beam training stage. Furthermore, the new method for identifying backup beam pairs is more effective to improve the spectral efficiencies of systems under blockage environments.

关键词： Training Structural beams Array signal processing Switches Radio frequency MIMO communication Antenna arrays

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Modelling and Forecasting of Commodity Trading Price

Modelling and Forecasting of Commodity Trading Price

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2018 2nd International Conference on Data Mining,Communications and Information Technology (DMCIT 2018)

作者： Jun Liu Yuan Tian Qing Yan Center for Data Science BUPT School of Information and Communication Engineering BUPT Beijing Laboratory of Advanced Information Networks BUPT Beijing Key Laboratory of Network System Architecture and Convergence BUPT

This paper proposes and improves a model for China's cotton reserves trading market,generates a more accurate price level table in contrast to the widely used China Cotton Association(CCA)'s table,and predicts the future trading price with this *** used is all 29895 trade records of cotton reserves from May,2016 to Sept,*** this paper,we firstly give a briefly introduction to the data as well as basic knowledge of cotton,especially the CCA's price level table as the target to improve *** then present a multiple linear regression with dummy variable model,which can reduce the error on predicting the trading price of current month,but still remains some problems such as the result shows a batch of cotton with better quality may get a lower *** we finally advance the model with multidimensional isotonic regression and more factors taken into *** last model could be used to predict the trade price of both current month and next month with approximately 4% mean absolute percentage error(MAPE).

关键词： CCA Modelling and Forecasting of Commodity Trading Price

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A Tri-band Bandpass Filter with Wide Stop Band Based on Quad-Mode Stub Loaded Resonator 5

A Tri-band Bandpass Filter with Wide Stop Band Based on Quad...

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The 5th International Symposium on Electromagnetic Compatibility

作者： Zhentao Zhao Shufang Li Jianfeng Zhu Meijun Qu Yang Kang First Research Institute of the Ministry of Public Security of PRC Beijing Key Laboratory of Network System Architecture and Convergence Beijing University of Posts and Telecommunications

ISBN: (纸本)9781509051861;9781509051854

This paper presents a tri-band bandpass filter with high design flexibility in symmetrical structure and a wide stopband by using quad-mode stub loaded ***-tostub coupling is introduced to split two identical modes and produce two transmission *** harmonic pass band can be typically eliminated by regularly embedding open-circuited stubs in the feeding structure without affecting the performance of the three passbands.A filter prototype is simulated to validate the proposed *** results show a desired wide upper stopband at 8.8 GHz with rejection better than 20 dB and three passbands are centered at 2.45 GHz,3.68 GHz,and 5.19 GHz respectively,which is applicable to WLAN and WiMAX applications.

关键词： Tri-band bandpass filter Stub-to-stub coupling open-circuitedstubs wide stopband

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A traffic prediction algorithm based on Bayesian spatio-temporal model in cellular network

A traffic prediction algorithm based on Bayesian spatio-temp...

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2017 International Symposium on Wireless Communication systems, ISWCS 2017

作者： Zhang, Zhen Liu, Fangfang Zeng, Zhimin beijing, Wen Zhao Laboratory of Advanced Information Networks Beijing Key Laboratory of Network System Architecture and Convergence Beijing University of Posts and Telecommunications Beijing100876 China

ISBN: (纸本)9781538629130

5G communication will bring a surge traffic in cellular network. The traffic in cellular network not only has strong variability by time, but also has strong spatio-temporal correlation, which brings large difficulty to predict. In order to make reasonable use of communication network resources, it is important to describe and predict the spatio-temporal information of traffic in cellular network. In this paper, we propose a traffic prediction algorithm based on Bayesian spatio-temporal model to predict the spatial distribution of traffic in cellular network at different moments via realistic traffic data of base stations (BSS). Firstly, we select Gaussian Predictive Process (GPP) as the basic model of the Bayesian spatio-temporal model and set proper prior distribution of the parameters. Secondly, we train the basic model by Gibbs sampling and the realistic traffic data to obtain the posterior distribution of the parameters. Then, we predict the spatio-temporal information of traffic in cellular network by Markov chain Monte Carlo (MCMC) computational techniques. Finally, we make theoretical analysis of prediction accuracy for the prediction results. The Index of Agreement (IA) of the prediction results in three different areas can reach 0.9 above, which indicate good prediction performance. The traffic prediction algorithm can be used to predict the spatio-temporal information of traffic in cellular network in different areas. © 2017 IEEE.

关键词： Forecasting

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An Improved Method for Orderly Funnel Analysis of Massive User Behavior Data

An Improved Method for Orderly Funnel Analysis of Massive Us...

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IEEE International Conference on network Infrastructure and Digital Content (IC-NIDC)

作者： Yipeng Jiang Fang Liu Qing Yan Zhengxiang Ke Beijing Key Laboratory of Network System Architecture and Convergence Beijing University of Posts and Telecommunications Beijing China The 28th Research Institute of China Electronics Technology Group Corporation

Funnel analysis is used to describe the conversation rate between user behavior. However, the funnel analysis method widely used currently has low-performance in process time. This paper presents an improved funnel analysis method based on the funnel analysis method. The method improvement includes presenting an improved funnel analysis algorithm having constant space complexity and linear time complexity, and utilizing the Spark framework to replace the Hive framework of the original method. The improvement method can be applied to analyze a large amount of data and real-time streaming data. The experimental results show that the performance of the improved method and the improved algorithm are efficient.

关键词： Time complexity Sparks Real-time systems Microsoft Windows Database languages Distributed databases

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