Integrating WAAS with LAAS to Avoid Signal Spoofing

Vis Sankaran and Donald Benson

Abstract:	The purpose of this paper is to show how a system satisfying strictest aviation requirements can be made immune to terrorist spoofing. The system combines Wide Area Augmentation System (WAAS) and Local Area Augmentation System (LAAS). It also uses secured independent signals for WAAS accuracy corrections that was recommended by Joint Program Office (JPO). WAAS is on the verge of becoming a full-scale development program for the Federal Aviation Administration (FAA) and was planned to be operational by 1997. However, national security concerns regarding the broadcast of GPS accuracy corrections on a global scale for WAAS was the subject of considerable discussions during early 1995. JPO has recommended “GPS dual use opportunities,” with secured independent WAAS uplink. In addition, WAAS can meet aviation requirements for all phases of flight down to CAT I precision approaches. But to get the requirements for CAT II/III precision approaches and landing (PAL), local area differentials are needed for augmenting with GPS. The concept, referred to as LAAS within the FAA, has been recommended as an additional augmentation. Here the differential technique is to locate a GPS monitor receiver at a surveyed reference site in the vicinity of an airport. The data is processed on the ground to determine pseudo- range corrections of GPS signals which are sent to the airborne receiver over a data link. By combining both WAAS and LAAS concepts, advantages of both systems could be merged for avoiding signal spoofing. This paper describes a conceptual development and integration of WAAS with LAAS to avoid signal spoofing for aviation requirements. Recommended configurations and generic specifications for interfacing WAAS, recently presented by JPO, with LAAS concept currently in study will be presented. In addition, how terrorist spoofing of the unsecured signals from the local area could be avoided by using the secured wide area signals will be discussed. A difference monitoring with a threshold will be provided. Finally, benefits of the integration concepts to provide uniformity in products regardless of manufacturer will be discussed.
Published in:	Proceedings of the 8th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1995) September 12 - 15, 1995 Palm Springs, CA
Pages:	677 - 684
Cite this article:	Sankaran, Vis, Benson, Donald, "Integrating WAAS with LAAS to Avoid Signal Spoofing," Proceedings of the 8th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1995), Palm Springs, CA, September 1995, pp. 677-684.
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