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GNSS rapid precise point positioning enhanced by low earth orbit satellites

Satellite Navigation 2023年第1期4卷 41-53,I0003页

作者： Ju Hong Rui Tu Pengfei Zhang Rui Zhang Junqiang Han Lihong Fan Siyao Wang Xiaochun Lu National Time Service Center Chinese Academy of SciencesShu Yuan RoadXi’an 710600China University of Chinese Academy of Sciences Yu Quan RoadBeijing 100049China

The low earth orbit(LEO)satellites can be used to efectively speed up Precise Point Positioning(PPP)*** this study,180 LEO satellites with a global distribution are simulated to evaluate their contribution to the PPP *** satellites can give more redundant observations and improve satellite geometric distributions,particularly for a single Global Navigation Satellite System(GNSS).The convergence speed of the PPP foat solution using the Global Positioning System(GPS,G)or BeiDou Navigation Satellite System(BDS,C)single system as well as the G/C/Galileo navigation satellite system(Galileo,E)/GLObal NAvigation Satellite System(GLONASS,R)combined system with LEO satellites added is improved by 90.0%,91.0%,and 90.7%,respectively,with respect to the system without LEO satellites *** introduced LEO observations to assist GNSS in PPP-AR(Ambiguity Resolution)and PPP-RTK(Real Time Kinematic).The success fx rate of a single system is signifcantly improved,and the Time-To-First-Fix(TTFF)of G and G/C/E is reduced by 86.4%and 82.8%,respectively,for the PPP-AR *** analyzed the positioning performance of LEO satellite assisted G/C/E PPP-RTK in the reference networks of diferent scales,namely diferent atmospheric delay interpolation *** success fx rate of the G/C/E combined system is improved from 86.8 to 94.9%,and the TTFF is reduced by 36.8%,with the addition of LEO satellites in the 57 km reference *** the 110 km reference network,the success fx rate of the G/C/E combined system is improved from 64.0 to 88.6%,and the TTFF is reduced by 32.1%.GNSS PPP-RTK with adding the LEO satellites in the reference networks of diferent scales shows obvious improvement because the atmospheric correlation decreases with increasing distance from the reference networks.

关键词： Precise point positioning low earth orbit LEO enhanced global navigation satellite system Rapid positioning

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Damage behavior of atomic oxygen on CVD SiC coating-modified carbon/carbon composite in low earth orbit environment

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Journal of Materials Science & Technology 2019年第12期35卷 2957-2965页

作者： Guanghai Liu Laifei Cheng Xingang Luan Jiaxin Zhang Science and Technology on Thermostructural Composite Materials Laboratory Northwestern Polytechnical University

In this work, samples of carbon/carbon(C/C) and chemical vapor deposited(CVD) SiC-coated C/C samples were investigated to understand the AO damage mechanism in low earth orbit(LEO) environment. The ground-based simulated atomic oxygen(AO) generator was employed. Results indicate that the CVD SiC coating exhibited improved radiation resistance properties against AO radiation as evidenced by a 16%better strength retention ratio, 60% less mass ablation, and increased strength stability. The magnitude of these influences affected the surface morphology, as observed by scanning electron microscopy(SEM)and surface resistance meter test results. The variations in the surface constituents were confirmed by X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS) results. The main products left on surface after AO exposure are SiO2 and SiCxOyfilm. Additionally, Si atoms are found to be the preferential reacting element in the SiC coating, and this process is accompanied by graphite precipitation, grain growth, and crack necking. Also, the damage mechanism of the AO-exposed SiC coating was revealed and is discussed.

关键词： Carbon/Carbon CVD SiC coating low earth orbit Atomic oxygen Exposure Stress

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low Altitude Satellite Constellation for Futuristic Aerial-Ground Communications

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Computer Modeling in Engineering & Sciences 2023年第8期136卷 1053-1089页

作者： Saifur Rahman Sabuj Mohammad Saadman Alam Majumder Haider Md Akbar Hossain Al-Sakib Khan Pathan Department of Electronic Engineering Hanbat National UniversityDaejeon34158South Korea Department of Electrical and Electronic Engineering Brac UniversityDhaka1212Bangladesh School of Business and Digital Technologies Manukau Institute of TechnologyManukau2241New Zealand Department of Computer Science and Engineering United International UniversityDhaka1212Bangladesh

This paper discusses the significance and prospects of low altitude small satellite aerial vehicles to ensure smooth aerial-ground communications for next-generation broadband *** achieve the generic goals of fifthgeneration and beyondwireless networks,the existing aerial network architecture needs to be *** detailed architecture of low altitude aerial networks and the challenges in resource management have been illustrated in this ***,we have studied the coordination between promising communication technologies and low altitude aerial networks to provide robust network *** talk about the techniques that can ensure userfriendly control and monitoring of the low altitude aerial networks to bring forth wireless broadband connectivity to a new *** the end,we highlight the future research directions of aerial-ground communications in terms of access technologies,machine learning,compressed sensing,and quantum communications.

关键词： Aerial-terrestrial network cognitive radio network cooperative communication high altitude platform low altitude platform low earth orbit satellite constellation unmanned aerial vehicle

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Determination of Total Electron Content at Equatorial Region—Thailand Using Radio Occultation Technique

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Atmospheric and Climate Sciences 2016年第2期6卷 319-328页

作者： Wasiu Akande Ahmed Ganiyu Ishola Agbaje Sikiru Yommy Aiyeola Bola O. Balogun Ngbede Joshua Ada Echoda Yakubu Abdullahi Onimago Taiwo Olunuga School of Instrumentation Science and Opto-Electronics Engineering Beihang University of Aeronautics and Astronautics Beijing China African Regional Centre for Space Science and Technology Education-English OAU Campus Ile-Ife Nigeria School of Electronics and Information Engineering Beihang University Beijing China

This paper investigates the total electron content (TEC) which is a major challenge to space and related industries, most especially in an equatorial region like Thailand within the geographical latitude 07°35'N - 20°17'N. This research was achieved using radio occultation data from COSMIC mission. The monthly, seasonal and annual TEC and electron density variation monitoring conducted during increasing solar activity from 2010 to 2013 due to changes and instability of ionospheric parameters. It was observed that electron density and TEC was predominant in summer season. Summer has the highest electron density and TEC values all through and the annual mean values keep on increasing within the period under consideration. In conclusion, ionospheric fluctuations and perturbations were observed to be at pick between the months of March and May. The results of the study demonstrated that ionospheric irregularities were steadily on the increase, confirming 24th solar cycle prediction by NASA and depended on many factors among the major ones which are located on the latitude, season and solar activity.

关键词： TEC Ionosphere GPS low earth orbit Radio Occultation Equatorial Zone

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AI-Based Optimization of Handover Strategy in Non-Terrestrial Networks

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ZTE Communications 2021年第4期19卷 98-104页

作者： ZHANG Chenchen ZHANG Nan CAO Wei TIAN Kaibo YANG Zhen State Key Laboratory of Mobile Network and Mobile Multimedia Technology ZTE CorporationShenzhen 518055China

Complicated radio resource management,e.g.,handover condition,will trouble the user in non-terrestrial networks due to the impact of high mobility and hierarchical layouts which co-exist with terrestrial networks or various platforms at different *** is necessary to optimize the handover strategy to reduce the signaling overhead and im⁃prove the service *** this paper,a new handover strategy is proposed based on the convolutional neural ***,the handover process is modeled as a directed *** a user knows its future signal strength,then he/she can search for the best handover strategy based on the ***,a convolutional neural network is used to extract the underlying regularity of the best handover strategies of different users,based on which any user can make near-optimal handover decisions according to its historical signal *** simulation shows that the proposed handover strategy can effi⁃ciently reduce the handover number while ensuring the signal strength.

关键词： convolutional neural network directed graph handover low earth orbit nonterrestrial network

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All-digital Carrier Frequency Tracking Method in LEO DS/SS Communication

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Semiconductor Photonics and Technology 2006年第2期12卷 126-130页

作者： XING Ke-fei YANG Jun ZHANG Chuan-sheng WANG Yue-ke Institute of Electromechanical Engineering and Automation NUDT Changsha 410073 CHN

An efficient method to track the carrier frequency which is recommended to use in low earth orbit(LEO) direct-sequence spread-spectrum(DS/SS) communication system is given. The carrier frequency drifts quicker in LEO DS/SS communication system, its tracking problem becomes much more important especially in digital receiver with the limits of physical shape and power. Under the condition of coarse carrier frequency synchronization, a digital tracking method based on least square method(LSM) is proved to be a quick, simple and efficient method. Numerical results and charts are given.

关键词： low earth orbit Direct-sequence spread- spectrum Carrier frequency tracking Least square method

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Influence Analysis of Multi-LEO Augmentation MEO Satellite orbit Determination under Regional Station Layout

Influence Analysis of Multi-LEO Augmentation MEO Satellite O...

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第十一届中国卫星导航年会

作者： Tian Zeng Lifen Sui Laiping Feng Xiaolin Jia State Key Laboratory of Geo-Information Engineering Information Engineering University Xi’an Research Institute of Surveying and Mapping

Since the ground monitoring stations layout for BeiDou navigation satellite system(BDS) is regional, the problem of bad orbit precision of BDS satellites needs to be resolved. Many scholars propose to

关键词： Reginal stations layout Combined orbit Determination low earth orbit Spaceborne GPS

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Simulation Analysis of LEO Satellite Navigation-augmented Property Based on Beidou-3

Simulation Analysis of LEO Satellite Navigation-augmented Pr...

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第十一届中国卫星导航年会

作者： Dixing Wang Xiaolin Jia Jiangwei Li School of Geology Engineering and Surveying Chang’an University Xi’an Research Institute of Surveying and Mapping School of Surveying and Mapping Science and Technology Xi ’an University of Science and Technology

low earth orbit(LEO) satellites have unique advantages in navigation enhancement due to their high signal strength and rapid geometric changes, has become a hot spot in the field of satellite navigati

关键词： low earth orbit Satellites Navigation Augmentation Constellation design Observation simulation

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