Researches Of Navigation Message Broadcasting Based On Fountain Coding

GNSS (Global Navigation Satellite System) has found wide applications in various areas. In order to enhance the robustness of navigation system, especially on deep fading channels, it is necessary to design applicable navigation message structure and to choose appropriate channel coding method. This thesis focuses on the message broadcasting based on fountain codes. The main contributions are as follows:1. A discussion is made on the channel modeling in deep fading environment caused by the shadowing. The channel is modeled as AWGN channel on the physical layer and erasure channel on the data link layer respectively. Then the simulations of LT codes on both channel models are conducted.2. Researches on the code-word construction and decoding scheme of short Raptor code are made. By the comparison of different code rate and code-word construction of the pre-codes, the deliberately chosen fountain-codes solution is presented on the basis of simulation results in deep fading situations.3. Aiming at the positioning problem in navigation deep fading environment, a new message broadcasting solution based on fountain code is proposed and the performance analysis is made. The results demonstrate that this solution provide higher positioning rate than traditional method in different erasure probabilities.4. With the fountain-coding-based message broadcasting scheme mentioned above, a solution for the transferring problem of Fountain-codes matrix is proposed. Analysis results demonstrate that the proposed method needs fewer redundancies and has better usability than traditional ones.