Interference Monitoring Investigations for WAAS

Karl W. Shallberg

Abstract:	The Wide Area Augmentation System (WAAS) is scheduled to conclude Phase 1 development efforts in 2000 and with FAA acceptance and commissioning, will be capable of providing navigation services for en route through precision approach. A key concern for GPS use in commercial navigation applications is the degree of unintentional interference for both user and ground segments. WAAS is currently addressing this concern for its ground segment by monitoring WAAS Reference Station (WRS) operating environments for RF interference as well as through development of increased mitigation performance in the WAAS reference receiver processing. This paper presents results of WAAS RF interference monitoring efforts and looks specifically at interference events investigated at the Anchorage Air Traffic Control Center and Billings Terminal Radar Approach Control Facility. Monitoring using the WAAS reference receiver indicated the presence of persistent L2 interference at these locations (the effectiveness of this particular receiver as an interference monitor was presented at ION-98), and follow-up RF surveys using more specialized equipment led to the identification of the offending signals. The paper also summarizes RF interference monitoring results for all WRSs. WAAS efforts using the reference receiver as an interference monitor have proven very successful, and this capability is currently under program consideration for integration into future phases of WAAS. With proper receiver outputs any GPS receiver can be utilized as an effective interference monitor, and therefore this paper should be beneficial to a wide audience. In particular, the Local Area Augmentation System community should find these results of interest since they will most likely require an interference monitoring capability of their own.
Published in:	Proceedings of the 2000 National Technical Meeting of The Institute of Navigation January 26 - 28, 2000 Pacific Hotel Disneyland Anaheim, CA
Pages:	91 - 97
Cite this article:	Shallberg, Karl W., "Interference Monitoring Investigations for WAAS," Proceedings of the 2000 National Technical Meeting of The Institute of Navigation, Anaheim, CA, January 2000, pp. 91-97.
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