Research On Transmission Technology Of Satellite-based Augmentation System

As an important component of global navigation satellite system(GNSS), the satellite-based augmentation system(SBAS) has invited widespread concerns of scholars at home and abroad. SBAS can provide additional information for users, thereby enhancing the positioning signal, navigation signal and the timing signal. The positioning accuracy, availability, continuity and integrity of navigation system can also be enhanced by SBAS. In SBAS, the information is transmitted to receivers through the satellite transmission link, therefore, the quality of the link directly determines the performance of the system. The author’s major contributions are outlined as follows:1. The structure of SBAS and its transmission link have been studied. Firstly, by studying the existing satellite-based augmentation systems,the parameters which are necessary when designing a transmission link are proposed. Secondly, according to the link budget which can provide minimum available signal-to-noise power ratio, a scheme of transmission link is designed. The scheme is based on the efficient channel coding, and theoretical analysis shows that it can support high transmission rate and low bit error rate for the system.2. The Quasi-Cyclic LDPC code has been studied. Firstly, the methods of constructing check matrix, encoding and decoding of QC-LDPC codes are discussed. Secondly, a 1/2 rate(2488,3,6) QC-LDPC code is designed by using the following two methods: constructing the check matrix based on circulate permutation matrices, and decoding based on belief propagation(BP) method. The simulation results show that the code can provide about 8.8d B coding gain in the 10-7 BER level.3. The key techniques of SBAS receiver have been studied. Firstly, according to a detailed discuss of commonly used signal acquisition methods, a weak signal acquisition scheme is put forward, which is based on the serial search and non coherent accumulation. Secondly, the theory of phase-locked loop is introduced,then a carrier and code tracking scheme for SBAS link is proposed, which using the Costas Loop and Delay Lock Loop(DLL). Thirdly, the bit synchronization and frame synchronization isrealized by detecting the correlation peak of Barker code. Finally, a simulation system is built and the relationship between different module in the flow chart is given, then the performance of the simulated SBAS link is analyzed.