The Research Of Satellite Channel Modeling And Simulation Method

The propagation characteristics of satellite affects multiple access method, encoding and modulation mode and power control technology, its relevant technology is one of the basic research for the satellite communication. In the process of signal transmitted from the satellite to earth receiving terminal, the signal will pass the free space, the exosphere, thermal layer, intermediate layer, stratospheric and tropospheric, there are many factors that affect the signal transmission which may change the amplitude and phase of the signal, the communication quality was degraded. In this background, the propagation characteristics of satellite channel was analyzed, then the principal component analysis and fuzzy clustering method were used to model multi-state Markov model. Finally, the implementation method and analyses channel performance of channel model were researched. The paper mainly includes the following points:(1) The relevant factors which may affect channel propagation characteristics were analyzed. The specific factors contain the free space loss, ionospheric scintillation, rain attenuation, gas absorption attenuation, clouds attenuation, depolarization effects, multipath and shadow effects. The following conclusions are summarized with the analyzing upon:The length of the free space is95%of total length in the satellite ground link, it is the first loss source. Ionospheric scintillation has a great relationship with quarter, wave frequency, observation point and solar activity, it may cause communication disruption under special astronomy conditions, so it is a key factor in the study of communication link. In stratosphere and troposphere, as the clouds, rain, air, mountains and other changes are complex and fast, so the multipath and shadow effect may arisen.(2) The determining method of key affecting factors of satellite channel based on principal component analysis is proposed. To resolve the problem that researchers relying on personal experience to identify key affecting factors is lack of theoretical basis, which may lead to the main affecting factors inaccurately determined and the actual propagation characteristics of the channel hardly reflected objectively by the established model, determining method of key affecting factors of satellite channel based on principal component analysis is proposed. The method analyzes the key affecting factors of satellite channel propagation characteristics from a theoretical point of view, which makes the established channel model more accurate and effective. (3) The determining method of the states number in satellite channel multi-state Markov model is proposed based on fuzzy clustering analysis. To solve the problem which are lack of theoretical basis, artificially divide satellite channel into several fixed states so that different researchers will get different conclusions in previous studies. Satellite channel multi-state Markov model method for determining the number of states based on fuzzy clustering analysis is proposed, this method can determine the states number of special link satellite channel from the mathematical point of view combining with F-distribution, which makes multi-state Markov model more scientific.(4) The improved method for calculating the Doppler frequency and the Doppler factor is proposed. To solve the problem that the characteristic of Doppler frequency, which is that the distance between adjacent frequency is equal to each other in traditional calculation method, it may cause the designed deterministic gaussian process resulting in a relatively small period, so that the corresponding gaussian shape resulting in a higher operational costs of power spectrum, sometimes failure defects occur, this method can produce the colored Gaussian noise with better performance and can better simulate satellite channel model.(5) The simulation method of classical satellite channel is researched. Theoretical channel model is the mathematical description of channel propagation characteristics. However, models which applied in research and production must be the models which can be realized by hardware or software, otherwise the models do not make any sense. Therefore, the realizing method of classical satellite channel model is studied in this paper. The measuring standard of channel statistical model is derived,such as first-order statistical properties (envelope statistical properties) and second-order statistical properties (average fading time and level crossing rate).