Channel modeling and data transmission in mobile satellite systems

The multipath fading in mobile satellite systems plagues the propagation medium by imposing random amplitude and phase variations on the transmission signal. However, the relative effect of an undesired random variation is reduced by the presence of a strong line-of-sight (l.o.s) component. In order to analyze the data transmission performance of the satellite-to-ground mobile channel, a Rician fading model is used. For this model the received multipath signal consists of the sum of a direct or (l.o.s) component and a fading component due to reflections from objects adjacent to the transmission path. Generally, when a data packet encounters a fade, it most likely contains errors and it will have to be retransmitted. Thus, the size of the packet is crucial to determine the performance of the channel. The present study finds for the first time the optimum packet size by applying an analytical model of the dynamics of the Rician channel. The performance criterion is based on the rate of information transfer through the network, the vehicle speed and the modulation fade margin