Method for Time-of-transmission Recovery Based on Assisted-GPS Positioning

As we all known, time-of-transmission cannot be worked out successfully when GPS receiver isn't able to accomplish the bit synchronization, frame synchronization and navigation data demodulation. In this proposed algorithm, the time-of-transmission was recovered through the iterative LMS equation and ambiguity search with the assistance data, including ephemeris information and satellite clock corrections etc. The algorithm was derived strictly and its main steps were introduced. Then, the selection of search factor ω was discussed and the restrictions for the initial errors of approximate location (150km) and receiver's clock bias (180s) were eliminated. The algorithm was proved to be valid using simulation results, which indicates that this method can be used in the real GPS application with poor received signal or partial signal.