Integrity Design and Updated Test Results for the Stanford LAAS Integrity Monitor Testbed

Gang Xie, Sam Pullen, Ming Luo, Per-Ludvig Normark, Dennis Akos, Jiyun Lee, Per Enge and Boris Pervan

Abstract:	The Stanford University Integrity Monitor Testbed (IMT) is a prototype of the Local Area Augmentation System (LAAS) Ground Facility (LGF) that is used to evaluate whether the LGF can meet the integrity requirements that apply to Category I aircraft precision approach. Because of the complexity of the monitoring algorithms, it is necessary to show that these requirements are met under a variety of possible failure situations. This paper explains the integrity monitor algorithms and fault-handling logic implemented in the IMT and reports the most recent nominal and failure test results with upgraded hardware. A significant fraction of the IMT code is dedicated to processing alert messages generated by different IMT monitor algorithms. Once these monitors begin flagging questionable measurements, several steps of logical reasoning and trial removals are required to determine which failed system elements are the source of the problem. This LGF function is known as "Executive Monitoring" (EXM). This paper describes in detail the EXM procedures implemented in the IMT and their role in meeting the LGF integrity and continuity requirements. For failure testing, two methods are used to inject failures into the IMT. One is to program a WelNavigate 40- channel GPS signal simulator to generate failed RF signals, which are then fed into the IMT. The other is to modify stored IMT receiver measurements collected under nominal conditions to inject failures after the fact and then have the IMT post-process these packets. Several recent results of IMT failure testing are reported. The results of these tests demonstrate that the IMT is capable of detecting and excluding failures in compliance with the LGF integrity requirements in the current LAAS Ground Facility Specification. Improved algorithms are under study to meet the much tighter requirements for Category III precision landings.
Published in:	Proceedings of the 57th Annual Meeting of The Institute of Navigation (2001) June 11 - 13, 2001 Albuquerque, NM
Pages:	681 - 693
Cite this article:	Xie, Gang, Pullen, Sam, Luo, Ming, Normark, Per-Ludvig, Akos, Dennis, Lee, Jiyun, Enge, Per, Pervan, Boris, "Integrity Design and Updated Test Results for the Stanford LAAS Integrity Monitor Testbed," Proceedings of the 57th Annual Meeting of The Institute of Navigation (2001), Albuquerque, NM, June 2001, pp. 681-693.
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