High Accuracy and High Availability Timing System by Using SBAS as Ranging Satellites

Masayuki Tanaka, Genta Shinohara, and Takahijo Ikeda

Abstract:	A market demand for timing signal with high accuracy and high availability is recently increasing. One of the solutions is to develop timing signal from GPS signal transmitted from GPS satellites. But those have following difficulties. 1) When the system has limited visual field of GPS satellites, continuous reception of satellite signal becomes unavailable due to GPS satellites being mobile satellites. This results in missing synchronization to the GPS signal which causes accuracy of timing signal to decrease. 2) Accuracy of timing signal reduces when using satellite with large pseudo range error. 3) Utilizing GPS itself is not an option when user prefers to use independent system controlled by their own country or from its military nature. We have solved the above by using SBAS signal transmitted from SBAS satellites which are geostationary satellites as a source for timing signal. This paper shows the key points for the timing performance evaluation when using SBAS signal as a timing source. 1) Investigation on SBAS satellites for message types and available area. 2) Performance comparison between SBAS signal and GPS signal for timing accuracy. 3) Performance comparison between MSAS and WAAS for timing accuracy. 4) Introduction of advantages of utilizing SBAS signal at satellite signal blockage condition. We have confirmed that SBAS signal can be utilized for timing source. Also it has been noted that auxiliary time information is required from external system such as GPS or other time data generating system because message transmitted from SBAS satellite does not have time information. The overall accuracy of the timing when using SBAS signal is less than GPS but it is for only several tenth of nano seconds and it high enough to be utilized.
Published in:	Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007) September 25 - 28, 2007 Fort Worth Convention Center Fort Worth, TX
Pages:	1983 - 1991
Cite this article:	Tanaka, Masayuki, Shinohara, Genta, Ikeda, Takahijo, "High Accuracy and High Availability Timing System by Using SBAS as Ranging Satellites," Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007), Fort Worth, TX, September 2007, pp. 1983-1991.
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