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An Improved Method of Ambiguity Resolution in GNSS Positioning

Chinese Journal of Electronics 2019年第1期28卷 215-222页

作者： GU Xiaoying zhu bocheng School of Electronics Engineering and Computer Science Peking University

High precision navigation with positioning accuracy of decimeter or even centimeter is becoming more and more important in many fields. Accurate carrier phase observations are the prerequisites for this requirement. Because they have much lower measurement noises than the code observations which are primarily used nowadays. However, the existence of integer ambiguity when counting cycles of carrier phases prohibits the straightforward application of the measurements. Once the integer ambiguity has been resolved, the application of carrier phase measurement is almost equivalent to pseudorange however with much higher precision. Therefore ambiguity resolution is key for fast and high precision positioning. The success rate of ambiguity resolution is affected by the ionospheric delay and observation noise. In previous methods, ionospheric errors are simply ignored. To resolve ambiguity reliably and quickly, we propose a modified method for precise point *** analyze the characteristics of the dual-frequency combinations of original observations and the ones with longer wavelengths and lower noises are preferable. The wide-lane and sub-wide-lane combinations with higher success rates are chosen for ambiguity resolution. Extra pseudoranges are included to eliminate the ionospheric delay which hampers ambiguity resolution seriously. After the combined ambiguities have been resolved, the original ambiguities of each frequency can be calculated from the linearly independent equations. Based on real Global positioning system(GPS) navigation data, performances of the modified method are tested and compared with that of the traditional method. The results show that the modified method is less affected by ionospheric delay and can obtain more accurate ambiguity resolution.

关键词： Global navigation satellite system Integer ambiguity resolution Precise point positioning High precision positioning

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Research of Fast Satellite Selection Algorithm for Multi-constellation

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Chinese Journal of Electronics 2016年第6期25卷 1172-1178页

作者： MENG Fanchen WANG Shan zhu bocheng School of Electronics Engineering and Computer Science Peking University

We propose a fast satellite selection algorithm for multi-constellation, which is based on both Newton's identities for Geometric dilution of precision(GDOP)fast computation and optimal satellite geometric distribution for less cycle participation. An effective closed-form formula is proposed for GDOP approximation, avoiding conventional matrix inversion and complexity. We reduce computational cycles with auxiliary optimal satellite geometric distribution, which improves the efficiency of realtime positioning under the combined action of both. Simulation results indicate that we can save more than 44% and99% computational complexity when selecting 7 satellites from 10 and 30 visible satellites respectively. The GDOP of proposed method is very close to optimal result, better than that of Quasi-Optimal algorithm.

关键词： Global navigation satellite system(GNSS) Geometric dilution of precision(GDOP) Newton’s identities Fast satellite selection

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A Convolutional Network Coding Oriented Four-Stage Contention Protocol for All-to-All Broadcasting Networks

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Chinese Journal of Electronics 2016年第1期25卷 192-198页

作者： LIU Yun WANG Shan zhu bocheng School of Electronics Engineering and Computer Science Peking University

Most practical networks are cyclic and demand Convolutional network coding(CNC). Researches on application of CNC in practical networks are still insufficient. Conventional graph theories cannot model the multicast channel properly. This paper introduces a multicast graph with multicast edges to model the multicast networks, and proposes a Multicast edge generation and max-flow detection(MEGAMAD) algorithm to approach the lower bound of necessary multicast edge number for a multicast network. Based on the algorithm we designed a new Media access control(MAC) protocol, the CNC oriented four-stage contention protocol(NC-FSCP) for the all-to-all broadcasting networks. The protocol runs a four stage reservation procedure to reserve time slots for encoded data transmission. Simulation proves that the reserved slot number approaches the lower bound for data dispersion in an all-to-all broadcasting network.

关键词： Convolutional network coding(CNC) MAC Multicast networks Max-flow min-cut

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An Improved Navigation Pseudolite Signal Structure Based on the Kasami Sequences and the Pulsing Scheme

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Chinese Journal of Electronics 2022年第2期31卷 220-226页

作者： TAO Lin SUN Junren LI Guangchen zhu bocheng School of Electronics Engineering and Computer Science Peking University

Pseudolites(PLs) are ground-based satellites, providing users with navigation ***, implementation of the PL system leads to the near-far problem. In this paper, we proposed an improved navigation PL signal structure of combing Kasami sequences and the pulsing scheme to mitigate the near-far effect. The pulse modulation method is adopted to ensure that the PLs transmit signals at different timeslots and reduce the PL signals' mutual interference. Additionally,we employ the small set of Kasami sequences with good cross-correlation properties to improve the anti-interference ability. A simulation test based on software is carried out to evaluate the performance of the proposed signal. The simulation proves that the improved PL signal has an impulsive power spectral density, makes it a feasible solution to mitigate the near-far effect, and performs better in the capture.

关键词： satellite navigation good cross-correlation properties improved navigation pseudolite signal structure interference suppression Kasami sequences pulse modulation method pulse modulation pulsing scheme PL system navigation solutions PL signals improved navigation PL signal structure anti-interference ability ground-based satellites

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A Probability Driven Quadri-Stage Contention Protocol for Mobile Ad Hoc Networks

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Chinese Journal of Electronics 2014年第3期23卷 591-597页

作者： LIU Yun MA Yongqiang zhu bocheng School of Electronics Engineering and Computer Science Peking University

The paper proposes a new contention based Time division multiple access(TDMA) Medium access control(MAC) protocol in wireless ad hoc networks,which can be termed Quadri-stage contention protocol(QSCP). The QSCP protocol is free of both the "hidden terminal" and the "exposed terminal" problems. It is distributive and arbitrarily scalable. In the dedicated contention stage, nodes exchange their "Normalized accumulation and dissipation rate of payload(NADROP)" messages in 2-hop neighborhood, and then run a contention probability calculation algorithm to decide the probability of sending a contention frame. The algorithm guarantees that the number of time slot reserved by a node is proportional to its NADROP value, which can remarkably improve the end-to-end throughput when network load is heavy, and is more efficient in energy consumption. The simulation results demonstrate that QSCP performs better than the existing protocols.

关键词： Mobile ad hoc network TDMA MAC Contention probability Data payload QSCP

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ASYMPTOTIC EFFICIENT ESTIMATION IN SEMIPARAMETRIC NONLINEAR REGRESSION MODELS

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Applied Mathematics(A Journal of Chinese Universities) 1999年第1期14卷 57-66页

作者： zhu Zhongyi\ Wei bocheng Dept. of Appl. Math. Southeast Univ. Nanjing

Abstract In this paper, the estimation method based on the “generalized profile likelihood” for the conditionally parametric models in the paper given by Severini and Wong (1992) is extended to fixed design semiparametric nonlinear regression *** these semiparametric nonlinear regression models,the resulting estimator of parametric component of the model is shown to be asymptotically efficient and the strong convergence rate of nonparametric component is *** results (for example Chen (1988),Gao & Zhao (1993), Rice (1986) et al.) are extended to fixed design semiparametric nonlinear regression models.

关键词： 1991 MR Subject Classification 62G07 62F35

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Reduced-order H∞ filtering for navigation with carrier phase

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Science China(Information Sciences) 2014年第2期57卷 27-36页

作者： LU ChenXi TAN YunHua zhu bocheng ZHOU Lezhu School of Electronics Engineering and Computer Science Peking University

A reduced-order H∞filtering algorithm for navigation with carrier phase is *** taking advantage of decoupling between filtering states in a navigation solution,this algorithm reduces computational cost and is robust in colored ***,the estimation precision is also improved by taking ambiguities as nuisance states when the filtering process *** to kinetic simulations under diferent noise are presented to demonstrate robustness and efciency of the algorithm.

关键词： navigation reduced-order H∞ filtering carrier phase

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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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On Finite Word Length Computing Error of Fixed-Point SAR Imaging Processing

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Chinese Journal of Electronics 2014年第3期23卷 645-648页

作者： XIE Yizhuang zhu bocheng YAN Wen ZHANG Weijie School of Information and Electronics Beijing Institute of Technology School of Electronics Engineering and Computer Science Peking University

Synthetic aperture radar(SAR) imaging system is generally realized by fixed-point with the purpose of reducing system implementation scale and enhancing real-time performance. Finite word length computing error of fixed-point SAR imaging system is studied. The characteristic of computing error in SAR imaging system is analyzed. A finite word length computing error model of SAR imaging system is built, by means of which the empirical formula of system’s output noise-to-signal ratio is derived. Based on the empirical formula, SAR imaging system processing word length is presented according to different processing granularities. The validity of this proposed finite word length computing error model of SAR imaging system is verified by system level fixed-point simulation.

关键词： Synthetic aperture radar(SAR) imaging Finite word length Analysis of computing error

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Attribute-Based Keyword Search over the Encrypted Blockchain

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Computer Modeling in Engineering & Sciences 2021年第7期128卷 269-282页

作者： Zhen Yang Hongao Zhang Haiyang Yu Zheng Li bocheng zhu Richard O.Sinnott Faculty of Information Technology Beijing University of TechnologyBeijing100124China School of Computing and Information Systems The University of MelbourneVictoria3010Australia

To address privacy concerns, data in the blockchain should be encrypted in advance to avoid data access fromall users in the blockchain. However, encrypted data cannot be directly retrieved, which hinders data sharing inthe blockchain. Several works have been proposed to deal with this problem. However, the data retrieval in theseschemes requires the participation of data owners and lacks finer-grained access control. In this paper, we proposean attribute-based keyword search scheme over the encrypted blockchain, which allows users to search encryptedfiles over the blockchain based on their attributes. In addition, we build a file chain structure to improve theefficiency of searching files with the same keyword. Security analysis proves the security of the proposed *** analysis and experimental results in performance evaluation show that our scheme is feasible andefficient.

关键词： Blockchain searchable encryption attribute-based encryption smart contract

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