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In designing a wireless communication system it is essential to have information about the characteristic of the associated communication channel. This thesis studies a channel characteristic experiment using a low earth orbit (LEO) satellite to measure mobile-LEO-satellite channels. We proposed a system architecture based on the pseudo-noise (PN) sequence technique whose feasibility was first demonstrated by Cox. However, due to the high dynamic environment many modifications and improvements have to be made. The proposed process of synchronization is a noncoherent system similar to that suggested by Cahn. We also address major design concerns, in particular, the frequency acquisition and tracking issue in the ground receiver. Since the LEO satellite travels with a relatively high and fast varying speed with respect to mobile terminals on the ground, a second-order automatic frequency control (AFC) loop is needed for fast frequency synchronization. Our simulation results show that frequency acquisition can be accomplished within 1 second when the received carrier-to-noise ratio (CNR) is 50 dB-Hz. The effect of multipath fading is investigated as well.
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