卫星信道建模及其仿真方法研究

发布时间：2019-05-27 19:28

【摘要】：卫星信道传播特性影响着信号的多址访问方式、编码方式、调制方式以及功率控制技术,其相关技术是卫星通信的基础性研究之一。信号由卫星传播到地面接收终端的过程中会依次经过外层空间、散逸层、热层、中间层、平流层和对流层,存在着很多影响着信号传输的因素,改变了信号的幅度和相位,使得通信质量降低。在此背景下,本文首先分析卫星信道的传播特性,采用主成分分析方法、模糊聚类方法建立多状态Markov模型,最后研究所建信道模型的实现方法并仿真分析信道性能,具体工作如下： (1)按信号传播的空间分布,依次分析了信道传播特性的相关影响因素。具体影响因素为自由空间损耗,散逸层、热层、中间层的电离层闪烁,平流层和对流层的降雨衰减、气体吸收衰减、云雾衰减、去极化效应、多径和阴影效应。总结得出以下几点结论：整个星地链路中,自由空间长度占总长度的95%以上,其产生的损耗为第一大损耗来源：电离层闪烁和季度、电波频率、观测点位置以及太阳活动有很大关系,在特殊天文条件下可能导致通信中断,是通信链路研究中必须要考虑的因素；平流层和对流层中由于云、雨、大气、山脉等变化极为复杂、快速,会导致信号产生多径及阴影效应。 (2)提出了基于主成分分析的卫星信道关键影响因素确定方法。针对传统信道建模中研究人员凭借个人经验确定关键影响因素缺乏理论依据,可能会导致主要影响因素确定不准确,所建立的模型不能客观反映实际信道传播特性的缺陷,提出了基于主成分分析的卫星信道关键影响因素确定方法。该方法从理论角度分析了影响卫星信道传播特性的关键因素,使得所建立的信道模型更加准确有效。 (3)提出了基于模糊聚类分析的卫星信道多状态Markov模型状态数确定方法。针对以前研究中,根据天气状况人为地把卫星信道分为固定的几种状态,没有理论依据,不同的研究人员会得到不同的结论,提出了基于模糊聚类分析的卫星信道多状态Markov模型状态数确定方法,该方法再结合F-分布可以从数学的角度确定特定链路卫星信道多状态Markov模型的状态数,使建立的多状态Markov模型更具有科学性。 (4)改进了多普勒系数及多普勒频率的计算方法。针对传统计算方法中多普勒频率具有相邻频率对之间的距离相等的特性,会造成所设计的确定性高斯过程得周期相对较小,相应的高斯形状功率谱运算成本较高,有时会发生失效的缺陷,提出了一种改进型多普勒系数及多普勒频率的计算方法,该方法产生的有色高斯噪声的性能较好,可以较好地仿真卫星信道模型。 (5)研究了经典卫星信道模型的仿真方法。信道理论模型是信道传播特性的数学描述,但应用在科研生产中的都是硬件或软件可实现的模型,否则没有意义。因此,本文研究了经典卫星信道模型的实现方法,同时推导了信道统计模型衡量标准：一阶统计特性(包络统计特性)和二阶统计特性(平均衰落时间和电平交叉率)。
[Abstract]:The transmission characteristics of the satellite channel influence the multiple access mode of the signal, the coding mode, the modulation mode and the power control technology, and the related technology is one of the basic research of satellite communication. The signal is transmitted from the satellite to the ground receiving terminal, through the outer space, the dissipation layer, the thermal layer, the middle layer, the stratosphere and the troposphere in turn, and there are many factors that affect the signal transmission, and the amplitude and the phase of the signal are changed, so that the communication quality is reduced. In this background, the paper first analyzes the propagation characteristics of the satellite channel, uses the principal component analysis method and the fuzzy clustering method to set up a multi-state Markov model, and finally, the method for realizing the channel model of the research institute and the simulation analysis channel performance are carried out, and the specific work is as follows: (1) According to the spatial distribution of the signal propagation, the influence of the channel propagation characteristics is analyzed in this order. the specific influencing factors are free space loss, dissipation layer, thermal layer, ionospheric scintillation of the intermediate layer, rainfall attenuation of the stratosphere and the troposphere, gas absorption attenuation, cloud attenuation, depolarization effect, multi-path and shadow effect, It should be concluded that in the whole satellite link, the free space length is over 95% of the total length, and the loss generated is the first large loss source: the ionospheric scintillation and the quarter, the radio wave frequency, the observation point position and the solar activity are very close It is a factor that must be taken into account in the study of communication links under special astronomical conditions; the changes in the stratosphere and the troposphere due to the changes of the cloud, the rain, the atmosphere, the mountains, etc. are extremely complex and fast, which can cause the signal to generate multi-path and shadow effect (2) The key influencing factors of the satellite channel based on principal component analysis are given. In the traditional channel modeling, the research personnel lack the theoretical basis for determining the key influencing factors by the personal experience, which may lead to the uncertainty of the main influencing factors, and the established model can not objectively reflect the actual channel propagation characteristics In this paper, the key influencing factors of the satellite channel based on the principal component analysis are put forward. In this paper, the key factors that influence the propagation characteristics of the satellite channel are analyzed from the theoretical angle, so that the established channel model is more accurate. In this paper, a multi-state Markov model of a satellite channel based on fuzzy clustering analysis is presented. In the past study, the satellite channel is divided into several fixed states according to the weather conditions, and there is no theoretical basis. The different researchers have different conclusions. The state of the multi-state Markov model of the satellite channel based on the fuzzy cluster analysis is put forward. The method comprises the following steps of: determining a state number of a multi-state Markov model of a specific link satellite channel from a mathematical angle by combining the F-distribution and the F-distribution, so that the established multi-state Markov model It is scientific. (4) The Doppler coefficient and Doppler are improved. The method for calculating the frequency is based on the characteristic that the distance between the adjacent frequency pairs of the Doppler frequency in the conventional calculation method is equal to the distance between the adjacent frequency pairs, so that the designed deterministic Gaussian process is relatively small, the corresponding Gaussian shape power spectrum operation cost is high, In this paper, an improved method for calculating the Doppler frequency and the Doppler frequency is proposed, and the performance of the colored Gaussian noise produced by the method is good, and it can be simulated well. True satellite channel model. (5) The classical satellite is studied. The channel model is a mathematical description of the channel propagation characteristics, but the application in the research and production is realized by hardware or software. In this paper, the method of the classical satellite channel model is studied, and the measures of the channel statistical model are derived. The first order statistical property (envelope statistical property) and the second order statistical property (average fading) are derived.
【学位授予单位】：南京信息工程大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN927.2

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