Research On Key Technology Of Assisted-beidou Positioning

With the growing demand of navigation positioning in weak satellite signal environments as well as urgent requirements for short time to first fix(TTFF), a high performance satellite positioning technology, Assisted Global Navigation Satellite System(A-GNSS), has been a hot research focus in the navigation field. In the paper, we discuss the key techniques of Assisted-Beidou positioning system.Firstly, assisted data help reduce the acquisition searching space. A method is adopted to estimate the shift of carrier frequency and pseudo-code phase, the uncertainty of the estimated value is also analyzed. Simulation shows that the clock bias and receiver dynamic are two important factors that cause the error of carrier frequency, the assist time precision and the assist position error are two key factors that led to the error of code phase.Secondly, the Assisted-Beidou software receiver related algorithm, such as acquisition and tracking algorithm, are designed and simulated. In addition, a strong signal assist weak signal method is used to compute the navigation data edge of the weak signal. With the navigation data edge, long coherent accumulation time becomes possible to acquire weak signals under complex environment.Finally, the influence of Beidou Geostationary Earth Orbit(GEO) and Non-GEO satellites to the A-Beidou receiver positioning accuracy is also discussed in the paper. analysis shows that GEO satellites help to improve the Assisted-Beidou receiver’s positioning precision, especially when there are a few numbers of acquired satellites.The paper comprehensively analyze the acquisition searching space and discuss the uncertainty of carrier frequency shift and pseudo-code phase of Assisted-Beidou positioning technology, key algorithm are also designed and simulated. All these work lays the research foundation for the development of relevant A-Beidou standards and the future applications of Assisted-Beidou technology in navigation industry.