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Robust Beamforming for Secured Wireless Power Transfer in MIMO Magnetic Resonant Coupling System:A Probabilistic Approach

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China Communications 2019年第1期16卷 97-107页

作者： Ling Xing Kaikai Deng feifei gao School of Information Engineering Henan University of Science and Technology Institute for Artificial Intelligence Tsinghua University(THUAI) State Key Lab of Intelligent Technologies and Systems Tsinghua University Beijing National Research Center for Information Science and Technology(BNRist) Department of Automation Tsinghua University

Wireless power transfer(WPT) to support mobile and portable devices is an emerging wireless *** all kinds of approaches,magnetic resonance coupling(MRC) is an excellent one for mid-range WPT,which provides better mobility,flexibility,and convenience due to its simplicity in hardware implementation and longer transmission *** this paper,we consider an MRCWPT system with multiple power transmitters,one intended power receiver and multiple unintended power *** investigate the probabilistic robust beamforming designs and provide efficient algorithms to achieve the local optimums under two different criteria,i.e.,total source power minimization problem and min-max unintended receiving power restriction *** the problems are quite typical in robust design situations,our proposed robust beamformers can be conveniently applied to other probabilistic robust design problems,thus reduce the complexity as well as improve the beamforming *** results demonstrate that the proposed algorithms can significantly improve the performance as well as the robustness of the WPT system.

关键词： magnetic resonance coupling wireless power transfer beamforming probabilistic robustness power security

An inverse problem in film/substrate indentation:extracting both the Young's modulus and thickness of films

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Acta Mechanica Sinica 2018年第6期34卷 1061-1071页

作者： Yin Zhang feifei gao Zhiyue Zheng Zhihai Cheng State Key Laboratory of Nonlinear Mechanics(LNM) Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials and Micro-Nano Devices Renmin University of ChinaBeijing 100872China

In an indentation test,the effective Young's modulus of a film/substrate bilayer heterostructure varies with the indentation depth,a phenomenon known as the substrate *** previous studies investigating this,only the Young's modulus of the film was *** the effective Young's modulus of a film/substrate structure is determined at a given contact depth,the Young's modulus of the film can be uniquely determined,i.e.,there is a one-to-one relation between the Young's modulus of the film and the film/substrate effective Young's ***,at times it is extremely challenging or even impossible to measure the film ***,the precise definition of the layer/film thickness for a two-dimensional material can be *** the current study,therefore,the thickness of the film and its Young's modulus are treated as two unknowns that must be *** the case with one unknown,there are infinite combinations of film thickness and Young's modulus which can yield the same effective Young's modulus for the film/*** inverse problem is formulated and solved to extract the Young's modulus and thickness of the film from the indentation depth-load *** accuracy and robustness of the inverse problem-solving method are also demonstrated.

关键词： Indentation test Film Substrate Inverse problem

Adversarial Training-Aided Time-Varying Channel Prediction for TDD/FDD Systems

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China Communications 2023年第6期20卷 100-115页

作者： Zhen Zhang Yuxiang Zhang Jianhua Zhang feifei gao State Key Lab of Networking and Switching Technology Beijing University of Posts and TelecommunicationsBeijing 100876China Institute for Artificial Intelligence Tsinghua UniversityBeijing 100084China

In this paper, a time-varying channel prediction method based on conditional generative adversarial network(CPcGAN) is proposed for time division duplexing/frequency division duplexing(TDD/FDD) systems. CPc GAN utilizes a discriminator to calculate the divergence between the predicted downlink channel state information(CSI) and the real sample distributions under a conditional constraint that is previous uplink CSI. The generator of CPcGAN learns the function relationship between the conditional constraint and the predicted downlink CSI and reduces the divergence between predicted CSI and real *** capability of CPcGAN fitting data distribution can capture the time-varying and multipath characteristics of the channel well. Considering the propagation characteristics of real channel, we further develop a channel prediction error indicator to determine whether the generator reaches the best state. Simulations show that the CPcGAN can obtain higher prediction accuracy and lower system bit error rate than the existing methods under the same user speeds.

关键词： channel prediction time-varying channel conditional generative adversarial network multipath channel deep learning

A Beam Stabilization Algorithm Based on Nonlinear Observer for Low Cost Satcom-on-the-Move

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China Communications 2014年第A1期11卷 16-22页

作者： TIAN Fanghao WANG Rong gao feifei YAO Minli Xi'anResearchInstituteofHighTechnology Xi'an710025China TsinghuaNationalLaboratoryforInformationScienceandTechnology(TNList) Beijing100084.China

A beam stabilization algorithm was proposed for low cost satcom-on-the-move （SOTM） to stabilize the vehicle-mounted antenna beam. The proposed algorithm utilizes the nonlinear observel to estimate the vehicle＇s attitude information based on inertial measurement unit. Then the estimated angles and angular velocities are used to stabilize the antenna beam. Experiment results show tha｜ the proposed algorithm can stabilize the antenna beam when the tracking information is available, indicating that it is competent to the SOTM system.

关键词： attitude estimation inertial measurementunit (IMU) nonlinear observ~ satellite communication.

Single Source Self-Screen Jamming Elimination and Target Detection for Distributed Dual Antennas Radar System

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China Communications 2017年第11期14卷 112-125页

作者： Qiliang Zhang feifei gao Qing Sun Xiaobo Wang Tsinghua National Laboratory for Information Science and Technology Beijing 100084 China Air Force Engineering University Xi'an 710051 China

Detecting target echo in the existence of self-screen jamming is a challenging work for radar system, especially when digital radio frequency memory(DRFM) technique is employed that mixes the jamming and target echo both in spatial and time-frequency domain. The conventional way to solve this problem would suffer from performance degradation when physical target(PT) and false target(FT) are superposed in time. In this paper, we propose a new spatial filter according to the different correlation characteristic between PT and FT. The filter takes the ratio of expected signal power to expected jamming and noise power as the objective function under the constant filter modulus constraint. The optimal filter coefficients are derived with a generalized rayleigh quotient approach. Moreover, we analytically compute the target detection probability and demonstrate the applicability of the proposed method to the correlation coefficient. Monte Carlo simulations are provided to corroborate the proposed studies. Furthermore, the proposed method has simple architecture and low computation complexity, making it easily applied in modern radar system.

关键词： self-screen jamming target correlation coefficient distributed dual antennas optimal filter target detection

Superimposed training for channel estimation of OFDM modulated amplify-and-forward relay networks

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Science China(Information Sciences) 2013年第10期56卷 55-66页

作者： ZHANG Han PAN DaRu CUI HaiXia gao feifei School of Physics and Telecommunication Engineering South China Normal University Tsinghua National Laboratory for Information Science and Technology National Mobile Communications Research Laboratory Southeast University

This paper is concerned with the problem of channel estimation for amplify-and-forward(AF)cooperative relay networks with orthogonal frequency division multiplexing(OFDM)*** algorithm is based on both the least square(LS)and minimum mean square error(MMSE)technique with a superimposed training ***,both the source and relay superimpose their own training signal onto data stream prior to transmission so as to estimate the separate channel state information of the source to relay link and the relay to destination *** also present the performance analysis and derive the approximated closed-form expressions for the MSE of separate channel estimation of source to relay link and the relay to destination link,respectively,from which we compute the optimal training signal as well as the relay power-amplifcation *** further improve the performance of channel estimation,we adopt a weighted average process to enhance the estimation performance over multiple OFDM blocks,from which we compute the optimal tracking *** results are provided to corroborate the proposed scheme.

关键词： channel estimation amplify-and-forward relay network OFDM superimposed training

Mainlobe jamming cancelation method for distributed monopulse arrays

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Science China(Information Sciences) 2018年第10期61卷 256-262页

作者： Qiliang ZHANG feifei gao Qing SUN Xiaobo WANG Tsinghua National Laboratory for Information Science and Technology Tsinghua University Air and Missile Defence College Air Force Engineering University

Dear editor,Array antennas, which are able to adaptively generate the mainlobe in the target direction and notches in the jamming directions, are usually employed by modern radars [1–3]. A notch is adaptively placed in the mainlobe direction when mainlobe jamming (MLJ) exists, which changes the shape of the mainlobe and decreases the antenna gain on the target echo. Hence, in this scenario, it makes detecting the target or estimating its direction more difficult, and the problem becomes more serious when MLJ is closer to the target.

关键词： Mainlobe jamming cancelation method for distributed monopulse arrays JSS MnP

Matched Filter Based Spectrum Sensing When Primary User Has Multiple Power Levels

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China Communications 2015年第2期12卷 21-31页

作者： ZHANG Xinzhi gao feifei CHAI Rong JIANG Tao Key Lab of Mobile Communication Technology Chongqing University of Posts and Telecommunications Department of Automation Tsinghua UniversityState Key Lab of Intelligent Technologies and SystemsTsinghua National Laboratory for Information Science and Technology(TNList) Beijing Wuhan National Laboratory for Optoelectronics Department of Electronic and InformationHuazhong University of Science and Technology

In this paper,we investigate the matched filter based spectrum sensing in a more reasonable cognitive radio(CR) scenario when the primary user(PU) has more than one transmit power levels,as regulated in most standards,i.e.,IEEE 802.11 Series,GSM,LTE,LTE-A,*** new multiple primary transmit power(MPTP) scenario is specialized by two different targets:detecting the presence of PU and identifying the power *** to the traditional binary sensing where only the presence of PU is checked,SU may attain more information about the primary network(making CR more "intelligent") and design the subsequent optimization *** key technology is the multiple hypothesis testing as opposed to the traditional binary hypothesis *** discuss two situations under whether the channel phase is known or not,and we derive the closed form solutions for decision regions and several performance metrics,from which some interesting phenomenons are observed and the related discussions are *** examples are provided to corroborate the proposed studies.

关键词： spectrum sensing power recognition matched filter multiple primary transmit power multiple hypothesis testing power mask

Variable partial-update NLMS algorithms with data-selective updating

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Science China(Information Sciences) 2014年第4期57卷 42-52页

作者： ZHU FengChao gao feifei YAO MinLi ZOU HongXing Tsinghua National Laboratory for Information Science and Technology Department of AutomationTsinghua University High-Tech Institute of Xi'an

We note that some existing algorithms are based on the normalized least-mean square(NLMS)algorithm and aim to reduce the computational complexity of NLMS all inherited from the solution of the same optimization problem,but with different constraints.A new constraint is analyzed to substitute an extra searching technique in the set-membership partial-update NLMS algorithm(SM-PU-NLMS)which aims to get a variable number of updating coefficients for a further reduction of computational *** get a closed form expression of the new constraint without extra searching technique to generate a novel set-membership variable-partial-update NLMS(SM-VPU-NLMS)*** that the SM-VPU-NLMS algorithm obtains a faster convergence and a smaller mean-squared error(MSE)than the existing *** is pointed out that the closed form expression can also be applied to the conventional variable-step-size partial-update NLMS(VSS-PU-NLMS)*** novel variable-step-size variable-partial-update NLMS(VSS-VPU-NLMS)algorithm is also verified to get a further computational complexity *** results verify that our analysis is reasonable and effective.

关键词： adaptive filter NLMS algorithm date-selective partial update set-membership filtering computational complexity