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Building a next generation Internet with source address validation architecture

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Science in china(Series F) 2008年第11期51卷 1681-1691页

作者： WU JianPing1,3,REN Gang1,3 & LI Xing2,3 1 department of Computer Science,tsinghua university,beijing 100084,china 2 department of electronic engineering,tsinghua university,beijing 100084,china 3 tsinghua National Laboratory for Information Science and Technology(TNList) ,beijing 100084,china department of Computer Science Tsinghua University Beijing 100084 China department of electronic engineering Tsinghua University Beijing 100084 China tsinghua National Laboratory for Information Science and Technology (TNList) Beijing 100084 China

The IP packet forwarding of current Internet is mainly destination based. In the forwarding process, the source IP address is not checked in most *** causes serious security, management and accounting problems. Based on the drastically increased IPv6 address space, a ＂source address validation architecture＂（SAVA） is proposed in this paper, which can guarantee that every packet received and forwarded holds an authenticated source IP address. The design goals of the architecture are lightweight, loose coupling, ＂multi-fence support＂ and incremental deployment. This paper discusses the design and implementation for the architecture, including inter-AS, intra-AS and local subnet. The performance and scalability of SAVA are described. This architecture is deployed into the CNGI-CERNET2 infrastructure a large-scale native IPv6 backbone network of the china Next Generation Internet project. We believe that the SAVA will help the transition to a new, more secure and dependable Internet.

关键词： IP source address validation network architecture network security

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Ultra-Broad-Band LiNbO3 Electro-Optic Modulators with Novel Complex Electrode

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Chinese Journal of Lasers 2000年第2期9卷 128-133页

作者： ZHOU Weiqin WU Boyu PENG Jihu GU Jinghua HU Jinyang (department of electronic engineering, tsinghua university, beijing 100084, china) 清华大学北京 100084

The characteristics of Z- cut LiNbO3optical modulators with novel complex electrode are discussed by using the finite element method （FEM） and studied experimentally in this paper. The travelling wave electrode consists of upper and lower parts. It can easily realize phase velocity matching between microwave and optical wave and drastically reduce microwave electrode loss. An electrooptic modulator with larger than 100 GHz bandwidth and half wave voltage 6 V is designed, fabricated and measured. Vπis 5. 1 V and the attenuation coefficient ac is 0. 3 dB/(cm· GHz1/2). The experimental results show that the modulator has great potentiality for expanding bandwidth.

关键词： electro-optic medulator LiNbO3 modulator travelling wave electrode complex electrode

On the TOPS mode spaceborne SAR

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Science china(Information Sciences) 2010年第2期53卷 367-378页

作者： BAI Xia 1 , SUN JinPing 2 , HONG Wen 3 & MAO ShiYi 2 1 department of electronic engineering, beijing Institute of Technology, beijing 100081, china 2 department of electronic engineering, Beihang university , beijing 100191, china 3 Institute of electronics,Chinese Academy of Sciences, beijing 100190, china 1. department of electronic engineering Beijing Institute of Technology Beijing 100081 China2. Department of Electronic Engineering Beihang University Beijing 100191 China3. Institute of Electronics Chinese Academy of Sciences Beijing 100190 China

TOPS (terrain observation by progressive scans) is a recently proposed SAR mode for wide swath acquisition, which aims at achieving the same coverage and resolution as the SCAN mode besides creating scalloping-free images. In this paper, a general SAR imaging model used in TOPS and other SAR modes is introduced, where the antenna sweep rate, Doppler centroid rate, illumination time and azimuth resolution are described by a parameter defined as the "mode factor". After analyzing the characteristics of TOPS signal, an algorithm based on chirp-z transform is proposed, in which a new de-rotation function is used. Simulation results validate the proposed algorithm.

关键词： synthetic aperture radar acquisition mode TOPS

Mapping and overlapping based carrier frequency searching technique for rapid GNSS long PN-code acquisition

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Science china(Information Sciences) 2010年第12期53卷 2642-2652页

作者： LI Hong ,LU MingQuan & FENG ZhenMing department of electronic engineering,tsinghua university,beijing 100084,china 1. department of electronic engineering Tsinghua University Beijing 100084 China

In global navigation satellite systems(GNSS),because of the long period and high chip rate of long pseudo-noise(PN) code,the rapid acquisition is hard to *** speed up search process,in the paper,a mapping and overlapping based carrier frequency searching technique is *** mapping incoming signals of the same interval to different carrier frequency cells and overlapping together the mapped incoming signals that correspond to the same code phase,the technique reduces the number of the cells to be *** effect of the technique on detection and mean acquisition time performance is *** is shown that the technique reduces the cells to be searched and shortens mean acquisition time at the expense of degrading detection *** technique is fit to the previously published acquisition methods and is capable of improving their mean acquisition time *** and simulation results validate the analysis.

关键词： carrier frequency cells mapping overlapping acquisition performance

Numerically stable method of signal subspace estimation based on multistage Wiener filter

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Science china(Information Sciences) 2010年第12期53卷 2620-2630页

作者： ZHUANG XueBin ,CUI XiaoWei,LU MingQuan & FENG ZhenMing department of electronic engineering,tsinghua university,beijing 100084,china 1. department of electronic engineering Tsinghua University Beijing 100084 China

In this paper,a numerically stable method of signal subspace estimation based on Householder multistage Wiener filter(HMSWF) is *** stability of the method lies on the fact that the Householder matrix in HMSWF ensures the unitary blocking operation and significantly strengthens the orthogonality of basis vectors,especially in the finite-precision *** the following,we analyze the numerical stability of HMSWF and MSWF based on the correlation subtractive structure(CSS-MSWF) by establishing the equivalence between the forward recursion of MSWF and the Arnoldi algorithm in numerical linear ***,the equivalence between HMSWF and the Householder QR decomposition(QRD) on the Krylov matrix underlying in MSWF is directly *** on the relationship,two theoretical upper bounds of the orthogonality error of basis vectors in signal subspace are obtained and it is demonstrated that the orthogonality of basis vectors based on HMSWF is perfectly preserved by the numerically well-behaved Householder matrix,and the corresponding signal subspace estimation is much more numerically stable than that based on *** show the numerical stability of the proposed method of signal subspace estimation by HMSWF.

关键词： multistage Wiener filter subspace estimation Householder transform numerical stability Arnoldi algorithm

Key parameter estimation for radar rotating object imaging with multi-aspect observations

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Science china(Information Sciences) 2010年第8期53卷 1641-1652页

作者： YE ChunMao, XU Jia , PENG YingNing & WANG XiuTan department of electronic engineering, tsinghua university, beijing 100084, china 1. department of electronic engineering Tsinghua University Beijing 100084 China

Rotating object model is commonly used for imaging analysis in high resolution radars such as the inverse synthetic aperture radar (ISAR). For a rotating object, it is known that multi-aspect observations can improve cross-range resolution with the known imaging geometry. For the non-cooperative rotating object with unknown imaging geometry, this paper proposes an integrated scheme to estimate the key parameters, e.g., the rotating velocity and the aspect angle difference between every two observations. Furthermore, convolution back-projection (CBP) method is applied to provide fused imaging result with improved resolution. Also, the accuracy of the ultimate parameter estimation is analyzed, which is strongly related with several important factors like position extraction error of scattering centers and so on. Finally, the results of numerical experiments are provided to demonstrate the effectiveness of the proposed method.

关键词： rotating objects multi-aspect observations fused imaging aspect angle difference

High-speed reconstruction for ultra-low resolution faces

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Science china(Information Sciences) 2012年第9期55卷 2102-2108页

作者： WANG Li ,CHEN JianSheng,HE JinPing & SU GuangDa department of electronic engineering,tsinghua university,beijing 100084,china 1. department of electronic engineering Tsinghua University Beijing 100084 China

In this paper,a learning-based high-speed reconstruction system for ultra-low resolution faces is implemented using a software/hardware co-design *** hardware component working at 60 MHz contains a field programmable gate array,which is reconfigured to contain parallel processing units,and multiple memories to create parallel *** hardware component effectively handles generating and sorting computationally intensive similarity *** solves the processing speed problem in learning-based super-resolution reconstruction for ultra-low resolution *** system can reconstruct faces using 8 × 6,16 × 12,and 32 × 24 sized images,with 4 × 4,8 × 8,or 16 × 16 times *** experimental results verify the effectiveness of our system in terms of both visual effect and low root mean square *** processing speed can be improved up to a maximum of 7900 times faster than a pure software implementation using C.

关键词： neighborhood image parallel computer template matching pixel compensation pipeline

Parameter estimation for SAR moving target in complex image domain

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Science china(Information Sciences) 2010年第4期53卷 854-866页

作者： ZUO Yu, XU Jia*, PENG YingNing & XIA XiangGen department of electronic engineering, tsinghua university, beijing 100084, china 1. department of electronic engineering Tsinghua University Beijing 100084 China

Based on the proposed parametric model of SAR ground moving target in the complex image domain, this paper derives the Cramer-Rao bounds (CRB) for the unknown model parameters estimation and obtains the inherent limitations for the moving target motion estimation in the SAR complex image domain. Firstly, the relationships are analyzed among the estimation performance and the target’s scattering intensity, Doppler parameters, motion parameters, as well as the power spectra of the target and the clutter. Furthermore, the parameter estimation performance is compared in the signal domain and the complex image domain (CID) to draw some useful conclusions. Besides, the reduction resolution processing is proposed to improve the parameter estimation, and its performance improvement is also presented with analytic expressions. For the homogeneous background, it is shown that the accurate parameter estimation and azimuth location may be realized for SAR ground moving target in the complex image domain. Finally, some numerical experiments are provided to demonstrate the effectiveness of the proposed methods.

关键词： synthetic aperture radar (SAR) moving target complex image domain parameter estimation Cramer-Rao bound (CRB) reduce resolution processing (RRP)

Performance Analysis of Two CFAR Detectors in Clutter Edge Situation

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Journal of Systems engineering and electronics 2001年第2期12卷 44-51页

作者： He You department of electronic engineering, Naval Aeronautical engineering Academy Yantai 264001, P. R. china Guan Jian department of electronic engineering, tsinghua university, beijing 100084, R R. china department of electronic engineering Naval Aeronautical Engineering Academy Yantai 264001 P. R. China department of electronic engineering Tsinghua University Beijing 100084 P. R. China

This paper studies the performance of the GOSGO and GOSSO CFAR detectors [1] in clutter edge situation. The authors derive the analytic expressions of the false alarm probabilities in that situation, analyze their performances against clutter edge, and compare them with the OS, CA, GO and SO detectors. The results show that GOSGO possesses better performance than GO for countering clutter, but the performance of GOSSO is very unideal.

关键词： Alarm systems Clutter (information theory) Gaussian noise (electronic) Signal to noise ratio White noise

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