ION GNSS 2012
Session D2: GPS & GLONASS Modernization

Title: Evaluation of Multi-constellation Advanced RAIM for Vertical Guidance Using Real GPS and GLONASS Signals Under Multiple Faults
Author(s): M. Choi, J. Blanch, T. Walter, Stanford University; D. Akos, University of Colorado Boulder; P. Enge, Stanford University
Date/Time: Wednesday, September 19, 2012, 4:46 p.m.
Room: Grand Ballroom West (Renaissance)

In the next years, two major changes in the GNSS environment could enable worldwide vertical guidance: the new L5 civil signal transmission and the launch of new GNSS constellation such as GLONASS, Galileo, and Compass. With these two enhancements receivers can mitigate the ionospheric induced error and be used in Advanced RAIM for vertical guidance. For this purpose, several Advanced RAIM (ARAIM) algorithms have been proposed and extensive evaluations [1], [2], [3] have been implemented in order to achieve global coverage of LPV200. Especially, previous work [4] has demonstrated the performance of multi-constellation ARAIM with real data for the first time, which meet the requirement of 35 meter Vertical Alert Limit (VAL). However, previous evaluation focused on accuracy and Vertical Protection Level (VPL) requirements. In addition, that effort only tested nominal case and one satellite fault situation. Therefore, additional effort is necessary for other requirements, which is addressed in [3], [5]. Moreover, tests with extended failure states, such as multiple satellite failure and a constellation failure, must be performed to test the ability of multi-constellation ARAIM to provide integrity.
In this paper, we will first present an accurate error model for both GPS and GLONASS using real data from our multi-constellation capable receiver for L1C/A, L2 semi-codeless, and L1, L2 band of GLONASS. Then we will implement all the requirements of LPV-200 in our ARAIM prototype. The four requirements are 4 m 95% accuracy, 10 m fault free 10-7 vertical position error, 15 m Effective Monitor Threshold, and 35m VPL. Then we will show the performance of multi-constellation ARAIM under additional injected fault states which include cases with more than two satellites failures and one entire constellation failure. This will be done using at least one month of GPS and GLONASS real measurement data with either actual faults or simulated faults added to the real data.

[1] M. Choi et al. "Advanced RAIM Demonstration using Four Months of Ground Data" Proceedings of ION ITM 2011, San Diego, CA, 2011.

[2] A. Ene et al. "Validation of Multiple Hypothesis RAIM Algorithm using Dual-Frequency GPS and Galileo Signals." Proceedings of the European Navigation Conference GNSS 2008, Toulouse, France.

[3] GNSS Evolutionary Architecture Study Phase II Report. http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/library/documents/

[4] M. Choi et al. "Demonstrations of Multi-Constellation Advanced RAIM for Vertical Guidance using GPS and GLONASS Signals" Proceedings of ION GNSS 2012, Portland, OR, 2012.

[5] J. Blanch et al. "A Proposal for Multi-Constellation Advanced RAIM for Vertical Guidance" Proceedings of ION GNSS 2012, Portland, OR, 2012.

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