近年来，以Starlink为代表的巨型星座计划相继被提出。相较于传统通信星座，巨型星座具有大规模、波束动态指向、节点数目多等一系列新的技术特征，导致巨型星座同频干扰场景分析遇到计算量激增、仿真时间过长等诸多问题。面向巨型星座场景，本文提出基于卫星分布概率的干扰分析方法，避免时间外推，降低干扰分析计算量。首先，建立了NGSO（Non-geostationary Orbit，非静止轨道）星座系统内同频共存场景下的干扰分析理论模型和卫星在地球站可视空域内分布概率的计算模型。推导了不同仰角下星座内卫星相位间隔与地球站视线张角之间的几何关系，从而给出了卫星出现概率在可视空域的分布规律，以及星座规模与相邻卫星视线张角的变化规律，此部分内容为后续内容提供了基础理论模型。其次，本文研究了单一构型场景下巨型星座的干扰分析方法。对于确定工作方式、通信参数及波束指向的卫星系统，其对同频卫星系统所产生的干扰仅与受扰地球站可视空域内施扰卫星的位置分布有关。因此，干扰的概率分布可通过施扰卫星的位置分布概率推导求解。基于该思路，本文建立了下行干扰场景下传统星座与巨型星座间同频干扰的系统模型，并提出了一种计算星座卫星分布的概率及星座间同频干扰概率分布的方法。此方法也可推广用于计算其他干扰评价指标的概率分布。第三，本文研究了复合构型场景下巨型星座的快速干扰分析方法。巨型星座通常由多种不同轨道高度的子星座组成，因此，提出一种适用于多种不同轨道高度、构型的复合星座的干扰分析方法。通过构造与多层星座卫星等分布概率的虚拟卫星，将多层星座的干扰简化等效为单层星座的干扰，从而降低干扰分析的计算量。在此基础上，以计算雨衰场景下载干噪比的例子，说明所提方法的可推广性。最后，本文研究了使用动态波束的巨型星座中，波束指向的概率分布及规律，以复合构型场景中的卫星位置概率模型为基础，研究子空域中卫星位置与波束指向的关系，以此获取波束指向概率分布。之后联合卫星位置分布概率计算干扰概率分布。
In recent years, mega-constellations represented by Starlink have been proposed successively. Compared with traditional communication constellations, mega-constellations possess a series of new technical characteristics such as large scale, dynamic beam pointing, and a masssive number of satellite nodes. It lead to many problems in the analysis of co-frequency interference scenarios of mega-constellations, such as excessive computation and long simulation time. To solve the above issues, the interference analysis method based on satellite distribution probability is proposed to avoid time extrapolation and reduce the computation amount of interference analysis for mega-constellations.Firstly, the theoretical model of interference analysis in the NGSO (Non-geostationary Orbit) constellation system under the coexistence scenario and the calculation model of the satellite distribution probability in the visual airspace of the earth station are established. The geometric relationship between the satellite phase interval in the constellation and the line-of-sight angle of the earth station at different elevation angles is deduced, which gives the distribution law of the satellite occurrence probability in the visible airspace. The variation law between constellation scale and line-of-sight angle of adjacent satellites is analyzed. This part provides the basic theoretical model for the subsequent contents.Secondly, the interference analysis method of mega-constellations in a single configuration is researched. For the satellite communication system whose operating mode, communication parameters and beam direction have been determined, the interference to the co-frequency satellite system is only related to the position distribution of interfering satellites in the visible airspace relative to the earth station. Hence, the probability distribution of interference can be solved by deriving the probability of interfering constellations satellites’ position. On this basis, the systematic model of the co-frequency interference between the traditional constellation and mega-constellation in the downlink interference scenario is established, and a method to calculate the probability of satellite distribution in the constellation and its interference is proposed. Besides, this method can also be extended to calculate other interference evaluation indexes.Thirdly, a fast interference analysis method of mega-constellations in composite configuration is studied. Mega-constellations usually consist of multiple sub-constellations with different orbital altitudes. Therefore, an interference analysis method is proposed for multiple constellation with different orbital altitudes and configurations. By constructing virtual satellites with equal distribution probability as the satellites of multi-layer constellations, the interference of multi-layer constellations is simplified and equated to the interference of single-layer constellations, thus reducing the computational amount of interference analysis. Based on this, the generalizability of the proposed method is illustrated with an example of calculating the interference to noise ratio for downloading rain fading scenarios. On the basis of this, an example to calculate the carrier to interference plus noise ratio in precipitation fade is given to illustrate the generalization of the proposed method.Finally, this thesis investigates the probability distribution and law of beam pointing in the mega-constellation using dynamic beams. Based on the probability model of satellite position in the composite configuration, it studies the relationship between satellite position and beam pointing in the sub-airspace to obtain the beam pointing probability distribution. Then the interference probability distribution is completed by combining the satellite position distribution probability.
