Study On Satellite Communication System’s Reliability Based On Invulnerability

Satellite communication has an irreplaceable role in the global personalcommunications and satellite navigation, and thus requires high reliability. The satellitecommunication system has the following features: high complication of structure,diversification and complexity of tasks undertaken, uncertain factors in the workingenvironment, vulnerability to malicious attacks from enemy. Therefore, it is veryimportant to study its invulnerability, which is one of its reliability indicators. In thisthesis, the invulnerability of the satellite communication system is studied in threeaspects, including constellation design, invulnerability assessment, and node importanceevaluation, so that its invulnerability can be greatly improved.The research works conducted in this thesis are summarized as follows:(1) A double-layer satellite constellation combined medium Earth orbit (MEO)satellites and low Earth orbit (LEO) satellites is proposed. For the design of the satellitecommunication system, the first and foremost task is constellation design. Analyzingquestions of the constellation design existing in the coverage of administrative divisionsin China along with invulnerability requirements, a double-layer satellite constellationcombined MEO satellites with LEO satellites is designed, which is really suitable forthe application in China. This constellation can not only meet the operationalrequirements of24hours a day to cover the administrative divisions in China, but alsohas certain invulnerability and can be upgraded.(2) The invulnerability assessment method based on the natural connectivity isdemonstrated to be applicable and practical for analyzing the invulnerability of satellitecommunication network. Three commonly used invulnerability assessment methods,including jump-plane nodes method, structural difference method, and naturalconnectivity method, are theoretically analyzed and comprehensively compared bydifferent calculation examples. Based on the above comparisons, it can be concludedthat the natural connectivity method has the advantages of accurate results and fastcalculation speed in the satellite communication network invulnerability assessment,and the method is very suitable for satellite communication network invulnerability analyses. Applying the proposed method to the designed MEO/LEO double-layersatellite constellation, the invulnerability performance of the system can be furtherimproved.(3) The principle, in which node importance evaluation method based on mutualinformation is got the highest priority in the research of satellite communicationnetwork node importance, is established. Due to the special structure of the satellitecommunication network in the satellite communication system, the importance of edgesin the network is not studied here, and the concerns are paid on the ordination of nodeimportance. The superiority of the proposed assessment method based on mutualinformation is demonstrated to be effectiveness by comparing it with other evaluationmethods. Using this method to quantitatively calculate the importance of satellite nodesof the designed double-layer satellite constellation network, important nodes of thenetwork can be easily identified. The satellites nodes in the constellation that need keymonitoring and protection in the later operation and maintenance are accordinglydetermined when limited resources are available.