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Time synchronization in communication networks based on the Beidou foundation enhancement system

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Science China(Technological Sciences) 2016年第1期59卷 9-15页

作者： liu Hui ZHANG RuFei liu jingnan ZHANG Ming GNSS Research Center Wuhan University

Communication networks rely on time synchronization information generated by base station equipment(either the Global Navigation Satellite System receiver or rubidium atomic clock) to enable wireless networking and communications. Meanwhile, the time synchronization among base stations depends on the Network Time Protocol. With the development of mobile communication systems, the corresponding time synchronization accuracy has increased as well. In this case, the use of sparsely distributed-high-precision synchronization points to synchronize time for an entire network with high precision is a key problem and is the foundation of the enhanced network communication. The current receiver equipment for China's digital synchronous network typically includes dedicated multi-channel GPS receivers for communication; however, with the development of GPS by the USA, network security has been destabilized and reliability is low. Nonetheless, network time synchronization based on Beidou satellite navigation system timing devices is an inevitable development trend for China's digital communications network with the establishment of the independently developed BDS, especially the implementation and improvement of the Beidou foundation enhancement system.

关键词： Beidou satellite navigation system precision timing time synchronization Beidou foundation enhancement system communication network time synchronization

On Applications of Selenodesy to Lunar Detection

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Geo-Spatial Information Science 2006年第3期9卷 162-170页

作者： WEI Erhu liu jingnan School of Geodesy and Geomatics Wuhan University 129 Luoyu Road Wuhan 430079 China.

According to the history of lunar detection, the relationship between selenodesy and lunar detection is reviewed , and the focus of the lunar detection and the lunar detection plan of China are summarized. The key tec... 详细信息

关键词： selenodesy lunar detection lunar orbit lunar gravity field lunar reference frame lunar control network lunar topography

Equivariant filtering framework for inertial-integrated navigation

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Satellite Navigation 2021年第1期2卷 434-450页

作者： Yarong Luo Chi Guo jingnan liu GNSS Research Center Wuhan UniversityWuhanChina Institute of Artificial Intelligence Wuhan UniversityWuhanChina

This paper proposes an Equivariant Filtering(EqF)framework for the inertial-integrated state *** the kin-ematic system of the inertial-integrated navigation can be naturally modeled on the matrix Lie group SE_(2)(3),the sym-metry of the Lie group can be exploited to design an equivariant filter which extends the invariant extended Kalman filtering on the group-affine system and overcomes the inconsitency issue of the traditional extend Kalman *** firstly formulate the inertial-integrated dynamics as the group-affine ***,we prove the left equivariant properties of the inertial-integrated ***,we design an equivariant filtering framework on the earth-centered earth-fixed frame and the local geodetic navigation *** experiments show the superiority of the proposed filters when confronting large misalignment angles in Global Navigation Satellite Navigation(GNSS)/Inertial Navigation System(INS)loosely integrated navigation experiments.

关键词： SE_(2)(3)matrix Lie group Inertial-integrated navigation Equivariant filtering Group-affine dynamic Invariant system Autonomous error

Structure and performance analysis of fusion positioning system with a single 5G station and a single GNSS satellite

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Geo-Spatial Information Science 2023年第1期26卷 94-106页

作者： Chi Guo Shufeng Qi Wenfei Guo Chenlong Deng jingnan liu GNSS Research Center Wuhan UniversityWuhanChina Hubei Luojia Laboratory WuhanChina

NaGlobal vigation Satellite System(GNSS)positioning technology is widely used for its high precision,global,and all-weather ***,in complex environments such as urban canyons,GNSS performance is often degraded due to signal occlusion and even fails to achieve positioning due to the insufficient visible *** of the characteristics of large band-width,low latency,and high Base Station(BS)density,the fifth-Generation mobile communication(5G)technology has gradually become a trend for positioning in cities while offering traditional communication *** supply the communication demands of the User Equipment(UE),only one BS is usually considered to establish a connection with the UE during the BS ***,the positioning accuracy with a single BS in urban canyons will be significantly *** further improve the positioning accuracy in such extreme scenarios,this paper proposes a simplified 5G/GNSS fusion positioning system architecture using observations from only a 5G BS and a GNSS *** this system,the GNSS receiver is mounted on the 5G BS,and the measurements provided by the receiver are used to form the differential code and complete the position *** positioning mathematical models of the system based on the original code and differential code are ***,the impacts of the measurements noise and the time synchronization error on the positioning accuracy are analyzed ***,the positioning performance is investigated by a set of simulation *** results show that under the existing 5G measurement noise and 2 m’s code measurement noise,the improvement of the differential code based fusion positioning compared with the 5G-only positioning is more than 32%,which is also about 6%higher than the original code based fusion ***,this improvement is not affected by the time synchronization error between the BS and the GNSS satellite.

关键词： The fifth-generation mobile communication(5G)positioning 5G/Global navigation satellite system(GNSS)fusion positioning differential code error analysis

Quality assessment of onboard GPS receiver and its combination with DORIS and SLR for Haiyang 2A precise orbit determination

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Science China Earth Sciences 2015年第1期58卷 138-150页

作者： GUO Jing ZHAO QiLe GUO Xiang liu XiangLin liu jingnan ZHOU Quan GNSS Research Center Wuhan University School of Geodesy and Geomatics Wuhan University Fugro Intersite B.V. Leidschendam 2263HWNetherlands Collaborative Innovation Center of Earth and Space Science Wuhan University Test and Assessment Research Center China Satellite Navigation Office

The GPS,DORIS,and SLR instruments are installed on Haiyang 2A(HY2A)altimetry satellite for Precise Orbit Determination(POD).Among these instruments,the codeless GPS receiver is the state-of-art Chinese indigenous onboard receiver,and it is the first one successfully used for Low Earth Orbit(LEO)***,the contribution assesses the performance of the receiver through an analysis of data integrity,numbers of all tracked and valid measurements as well as multipath *** receiver generally shows good performance and quality despite a few *** example,L2 observations are often missing in low elevations,particularly during the ascent of GPS satellites,and the multipath errors of P1 show a slightly abnormal ***,the PCO(Phase Center Offset)and PCV(Phase Center Variation)of the antenna of the GPS receiver are determined in this contribution.A significant leap for Z-component of PCO up to-1.2 cm has been found on 10 October ***,the obtained PCO and PCV maps are used for GPS only POD *** post-fit residuals of ionosphere-free phase combinations reduce almost 50%,and the radial orbit differences with respect to CNES(Centre National d’Etudes Spatiales)Precise Orbit Ephemeris(POEs)improve about 13.9%.The orbits are validated using the SLR data,and the RMS of SLR Observed minus Computed(O-C)residuals reduces from 17.5 to 15.9 *** improvements are with respect to the orbits determined without PCO and ***,six types of solutions are determined for HY2A satellite using different combinations of GPS,DORIS,and SLR *** of SLR O-C residuals and cross-comparison of orbits obtained in the contribution and the CNES POEs indicate that the radial accuracy of these orbits is at the 1.0 cm level for HY2A orbit solutions,which is much better than the scientific requirements of this *** is noticed that the GPS observations dominate the achievable accuracy of POD,and the combination of multiple types of observation

关键词： Haiyang 2A GPS receiver multipath precise orbit determination phase center offset phase center variations DORIS SLR

Chinese Surveying and Control Network for Earth-Orbit Satellites and Deep Space Detection

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Geo-Spatial Information Science 2006年第1期9卷 6-12,37页

作者： WEI Erhu liu jingnan SHI Chuang School of Geodesy and Geomatics Wuhan University 129 Luoyu Road Wuhan 430079 China

The relationship between the surveying and contro l network(CSN) for earth-orbit satellite and spatial geodesy, and the relationshi p between the CSN for deep space celestial bodies and detectors, and deep space detection are briefly summarized, and so are the basic technical needs of the de ep space surveying and control network(DSN). Then, the techniques, the constitue nts and the distributing of Chinese satellite CSN (CSCSN) and other radio observ ing establishments in China are introduced. Lastly, with the primary CSCSN and o ther observing establishments, some projects for China to rebuild a more perfect CSCSN, and to establish a DSN are analyzed and stated.

关键词： satellite surveying and control network DSN microwave radio radar LLR DSCCs radio observation space-based station

Study on compound ultra-precision alignment technique

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仪器仪表学报 2007年第10期28卷 1741-1745页

作者： Zhang Jinlong Yang Ankang liu jingnan Yoshiyuki Uchidas College of Electrical and Automatic Engineering Nanjing Normal Univ. Nanjing 210042 China Automation College Southeast Univ. Nanjing 210096 China Department of lnformation Network Engineering Aichi Institute of Technology Toyoda 470-0392 Japan

A nano-displacement measurement system with duo-gratings is analyzed by using optics theory,a math- ematic model for the system is established,and the characteristic of laser Moirésignals is studied through CAD simu- *** improve signal sensitivity and positioning accuracy,two methods of precision positioning are brought for- ward:differential Moirépositioning method and modified Moirépositioning method.A compound control system for precision positioning is set up by combining these 2 Moiréalignment methods,in which the modified Moiréalignment technique is used for coarse alignment and the differential Moiréalignment technique is used for fine alignment,and the system obtains positioning accuracy of±10 nm in±500μm positioning range with shot response time.

关键词：信号超精密排列技术纳米位移测量系统微分混合排列光学

Effects of errors-in-variables on the internal and external reliability measures

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Geodesy and Geodynamics 2024年第6期15卷 568-581页

作者： Yanxiong liu Yun Shi Peiliang Xu Wenxian Zeng jingnan liu First Institute of Oceanography Ministry of Natural ResourcesQingdao 266061China School of Geomatics Xi'an University of Science and TechnologyXi'an 710048China Disaster Prevention Research Institute Kyoto UniversityUjiKyoto 611-0011Japan School of Geodesy and Geomatics Wuhan UniversityWuhan 430079China Research Center of GNSS Wuhan UniversityWuhan 430079China

The reliability theory has been an important element of the classical geodetic adjustment theory and methods in the linear Gauss-Markov model. Although errors-in-variables(EIV) models have been intensively investigated, little has been done about reliability theory for EIV models. This paper first investigates the effect of a random coefficient matrix A on the conventional geodetic reliability measures as if the coefficient matrix were deterministic. The effects of such geodetic internal and external reliability measures due to the randomness of the coefficient matrix are worked out, which are shown to depend not only on the noise level of the random elements of A but also on the values of parameters. An alternative, linear approximate reliability theory is accordingly developed for use in EIV models. Both the EIV-affected reliability measures and the corresponding linear approximate measures fully account for the random errors of both the coefficient matrix and the observations, though formulated in a slightly different way. Numerical experiments have been carried to demonstrate the effects of errors-in-variables on reliability measures and compared with the conventional Baarda's reliability measures. The simulations have confirmed our theoretical results that the EIV-reliability measures depend on both the noise level of A and the parameter values. The larger the noise level of A, the larger the EIV-affected internal and external reliability measures;the larger the parameters,the larger the EIV-affected internal and external reliability measures.

关键词： Weighted least squares Errors-in-variables model Nonlinear adjustment Total least squares Reliability theory

Semi-analytical assessment of the relative accuracy of the GNSS/INS in railway track irregularity measurements

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Satellite Navigation 2021年第1期2卷 352-367页

作者： Qijin Chen Quan Zhang Xiaoji Niu jingnan liu GNSS Research Center Wuhan UniversityWuhanChina Collaborative Innovation Center of Geospatial Technology Wuhan UniversityWuhanChina Artificial Intelligence Institute Wuhan UniversityWuhanChina.

An aided Inertial Navigation System(INS)is increasingly exploited in precise engineering surveying,such as railway track irregularity measurement,where a high relative measurement accuracy rather than absolute accuracy is ***,how to evaluate the relative measurement accuracy of the aided INS has rarely been *** address this problem with a semi-analytical method to analyze the relative measurement error propagation of the Global Navigation Satellite System(GNSS)and INS integrated system,specifically for the railway track irregularity measurement *** GNSS/INS integration in this application is simplified as a linear time-invariant stochastic system driven only by white Gaussian noise,and an analytical solution for the navigation errors in the Laplace domain is obtained by analyzing the resulting steady-state Kalman ***,a time series of the error is obtained through a subsequent Monte Carlo simulation based on the derived error propagation *** proposed analysis method is then validated through data simulation and field *** results indicate that a 1 mm accuracy in measuring the track irregularity is achievable for the GNSS/INS integrated ***,the influences of the dominant inertial sensor errors on the final measurement accuracy are analyzed quantitatively and discussed comprehensively.

关键词： Inertial surveying Relative measurement accuracy Error propagation modeling Steady-state Kalman filter Precise engineering surveying