Research And Simulation Realization Of Broadband Satellite Mobile Channel

With the rapid development of land mobile communication systems, the fourth-generation mobile communication system has become commercial, the fifth-generation mobile communication systems are being studied comprehensively, and the data transmission rate and carrier frequency are constantly increasing. Meanwhile, satellite mobile communication system has also developed to the third-generation, providing high-speed broadband Internet access and wireless multimedia communications services. Satellite mobile communication system is moving toward broadband signal and high frequency carrier. The wideband signals go through frequency selective fading, which causes inter-symbol interference, and signal waveform distortion. However during the information transmission through the atmosphere with the ground station, the high-frequency carrier in the satellite system will inevitably be affected by atmospheric absorption loss, rain attenuation, ionospheric scintillation etc. Therefore, to improve the service quality of broadband satellite systems, studying the characteristics of broadband mobile satellite channel is of significance.Based on the introduction above, this thesis studies the characteristics of broadband mobile satellite channel from the following aspects.Firstly, this thesis analyses the radio wave propagation mechanisms, including multipath effects, shadowing, Doppler frequency shift and their impacts on radio signal. It also studies the effects of atmospheric loss and rain attenuation in the satellite-ground-station transmitting process of the high-frequency signal. To quantify these effects, statistical modeling and computer simulation of rainfall attenuation in Chengdu are completed. The thesis has accomplished a comparative analysis of different influences of communication elevation, the operating frequency and rainfall intensity on rain attenuation, and given the Rician, Rayleigh and Lognormal probability distribution function derivation and its physical meaning.Secondly, the thesis clarifies the difference between broadband satellite mobile channel and narrowband satellite mobile channel. With the frequency selective fading of broadband signal, we provide the impulse response function of broadband satellite mobile channel based on wide sense stationary uncorrelated scattering model and build the broadband satellite channel model on the basis of tap delay line principle. Then we research how to simulate flat fading channel according to the method of shaping filter, sine wave superposition and random number generation, afterwards the computer simulation are implemented. Furthermore, we randomize the frequency and phase of every sinusoid to improve the simulating performance. Moreover, the thesis verifies the validity of the proposed model with the analysis including the simulation of time-domain and frequency-domain and the comparison with statistical properties of measured data.Finally, the thesis designs and realizes broadband satellite mobile channel simulator based on STK and MATLAB GUI. The channel model of the simulator is based on the one established in this thesis, with the secondary development of STK satellite toolkit, using its powerful reporting capabilities in real-time analysis to calculate the elevation of satellite communications, Doppler shift and satellite ground link distance, and through co-simulation with MATLAB, these data are transmitted in real time to the channel simulator. In this way, the satellite orbit can be observed clearly, at the same time, its channel transmission characteristics and link characteristics can be analyzed on the channel simulator, thus it has high practical value.