Research Of Spaceborne VDES Key Technologies Applied To Navigation In Polar Region

VDES(VHF data exchange system)is the new generation maritime communication system proposed by the IALA(International Association of marine aids to navigation and Lighthouse Authorities),which provides data exchange services for navigation ships all over the world.The VDES composed of shore based VDES and spaceborne VDES realizes seamless coverage all over the world.Spaceborne VDES is a supplementary part of VDES ground network,which mainly covers high latitude polar regions and far sea regions that are difficult to be covered by ground network.The key technologies of spaceborne VDES applied to polar navigation can not only meet the communication needs of polar navigation ships,but also improve the common throughput of spaceborne VDES system.Therefore,the research on the key technology of spaceborne VDES applied to polar navigation is of great significance.On the basis of summarizing the research status of spaceborne VDES and its key technologies at home and abroad,the key technologies of spaceborne VDES applied to polar navigation are studied and verified.The main work is as follows:1.Architecture of space-ground integrated VDES is constructed,the spaceborne VDES protocol stack is designed,the key technologies of spaceborne VDES protocol stack applied to polar navigation are analyzed,and the spaceborne VDES communication service flows are given;2.A design scheme of polar orbit constellation with complete coverage in polar region is proposed.According to the coverage characteristics of different constellations and under the condition of ensuring the requirements of spaceborne VDES transmission delay,the spaceborne VDES satellite constellation applied to polar navigation is designed,and the coverage characteristics and transmission delay of the constellation are verified by using STK and MATLAB simulation software.3.A improved satellite angle based TDMA named ISAB-TDMA(Improved Satellite Angle Based-TDMA)downlink scheme based on satellite azimuth is proposed.By comprehensively considering the user’s real-time channel quality and the satellite azimuth that stops serving the user,the scheme considers the azimuth of the satellite that stops serving users,ensures that all users within the coverage of vdes satellite can receive services fairly,and improves the public throughput of spaceborne vdes without affecting the average throughput.The common throughput and rate distribution of the scheme are verified by using MATLAB simulation software4.Based on the wireless communication platform of Znyq and Cortex A9,using C language,the link layer protocol of spaceborne VDES ground controlling station,spaceborne VDES satellite station and spaceborne VDES ship terminal module are developed,which realizes the functions of spaceborne VDES synchronization,terminal Satellite positioning information information reporting,uplink packet data transmission and downlink packet data transmission of spaceborne VDES applied topolar navigation.5.The test system of key technologies of spaceborne VDES applied to polar navigation is built,and the key technologies of spaceborne VDES applied to polar navigation are tested.The test results show that the function and performance of spaceborne VDES system based on space-ground integrated can meet the requirements of spaceborne VDES applied to polar navigation.