| With the rapid development of satellite positioning technology in China, the Beidou satellite navigation system researched and developed by our country has started to provide much of the Asia-Pacific region with services such as continuous passive location, optimal route guidance, precise timing and short message communication. Time to First Fix(TTFF) is one of the important indexes to show a navigation receiver’s fast positioning capability and it is closely related to the navigation receiver’s cold-start, warm-start or hot-start strategy, location algorithm and data processing work flow.With a study and a comparison between the Beidou system and other satellite navigation systems, this thesis makes an analysis about some major approaches in this field both at home and abroad in reducing the time to first fix. Based on its unique characteristics, this paper proposes a new start strategy especially for the Beidou satellite navigation system. It can not only make a reasonable allocation for different channels to search for the satellite signals by making a full use of the receiver’s hardware resources, but also narrow down the receiver’s research scope and increase the success rate to capture the satellite signals with all the known information. The research result shows that the new start strategy can effectively help to shorten the navigation receiver’s time to first fix and bring about a fast positioning.With the finding of the new start strategy and based on the study of both satellite positioning algorithm and the data processing work flow, the author introduces a quick way predicting the satellite signal launch time. With a known valid ephemeris, the new method may be able to omit the frame synchronization process, which can lead to a fast positioning. The experimental data discloses that after applied in an authentication mechanism, the possibility of a large error is excluded and it shows that the new start method may realize a quick and accurate positioning. |
PDF Full Text Request