Chapter 52 Research on A-GPS Rapid Positioning Algorithm Based on Doppler Positioning

摘要

The time to first fix (TTFF) of conventional GPS receiver need one minute or more in the case of autonomous cold start, when in weak signal environments like indoors or urban canyons, even tens of minutes are difficult to achieve the TTFF. Assisted Global Positioning System provided ephemeris, a priori time and a priori position for a A-GPS receiver through the cellular network base station to solve the weak signal positioning problem, the process of observation satellite and decoding ephemeris move to A-GPS reference station and a location server to complete. From initial acquisition to frame synchronization need to go through its correlation lock, phase lock, the bit synchronization process, When the signal is very weak that cannot achieve frame synchronization and demodulation satellite TOW, the conventional algorithm cannot achieve positioning solution. The A-GPS fast positioning algorithm combine the Doppler positioning and reconstructing full pseudoranges method presented in this paper, reconstructing full pseudoranges method elimination the common bias implied in integer millisecond pseudoranges to avoiding the integer millisecond ambiguity problem in reconstructing launch time method due to common bias and measurement error, Doppler positioning solution guarantees to provided a initial position and time error less than 0.5 light-ms, so the A-GPS rapid positioning resolved in the coarse time and rough location condition.