Solutions to Issues of GBAS using SBAS Ranging Source Signals

Susumu Saito, Naoki Fujii, Kazushi Suzuki, Takeshi Ono

Abstract:	This paper presents the simulation results of SBAS (Satellite- Based Augmentation System) ranging source signals effect on GBAS (Ground-Based Augmentation System) with real data observed by our GBAS test-bed and solutions for issues of GBAS caused from using SBAS ranging source signals. ENRI has been developing and evaluating GBAS for GNSS (Global Navigation Satellite System). The test-bed of GBAS is installed at Sendai Airport in Japan. The GBAS ground facility that is gradually upgraded in about these ten years. A modification in fiscal year of 2005 enabled the test-bed of GBAS to process SBAS ranging signals in addition to GPS ranging signals. MSAS (MTSAT Satellitebased Augmentation System) has been available in Japan as GBAS ranging sources and analysis for GBAS using SBAS ranging source signals were conducted. We carried out simulations to evaluate the performance of GBAS with SBAS ranging source signals using the real data of GPS and SBAS signals. The results showed that the direct use of SBAS ranging source signals degraded spr,grd considerably. However, this issue can be solved by appropriately weighting on GPS and SBAS ranging source signals in receiver clock-offset compensation without introducing additional error in GBAS compared with the case without SBAS. We showed that SBAS ranging source signals can rather improve GBAS performance in certain GPS satellite distributions with some unavailable GPS satellites. Using SBAS ranging source signals may introduce additional integrity risks to GBAS. If ephemeris data used by an airborne GBAS equipment with SBAS ranging source signals was different from that used by a GBAS ground facility, the airborne user calculates its position with error caused by inconsistency of SBAS MT-9 data. The difference between GPS ephemeris and SBAS GEO navigation message (SBAS MT-9) are examined in our analysis. Current specifications of RTCA documents and ICAO (International Civil Aviation Organization) document provide the synchronization protocol of GPS ephemeris data for the air and ground, but they do not mention the synchronization protocol of SBAS MT-9. We propose the solution for the SBAS MT (Message Type)-9 synchronization issues in this paper without changing SARPs, which makes no issues of GBAS positioning using SBAS ranging source signals.
Published in:	Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008) September 16 - 19, 2008 Savannah International Convention Center Savannah, GA
Pages:	2894 - 2900
Cite this article:	Saito, Susumu, Fujii, Naoki, Suzuki, Kazushi, Ono, Takeshi, "Solutions to Issues of GBAS using SBAS Ranging Source Signals," Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008), Savannah, GA, September 2008, pp. 2894-2900.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In