GPS Interference: A Question of Inetgrity?

Trent Skidmore and Fan Liu

Abstract:	Potential interference to GPS and the Federal Aviation Administration’s Wide Area and Local Area Augmentation Systems (WAAS & LAAS) is an important consideration in the design and certification of both ground reference stations and airborne sensor units. The RTCA Minimum Operational Performance Standard (MOPS) for Global Positioning System/Wide Area Augmentation System Airborne Equipment specifies a series of recommended tests to be used by manufacturers when demonstrating equipment compliance under the required interference conditions. One of the key tests in the MOPS is the interference integrity test (IIT). This test is designed to stress the GPSIWAAS sensors in order to assure that no harmful (hazardously) misleading information will be output by the receiver. In practical terms, this test is used to verify that if a GPSAVAAS sensor encounters interference in excess of the normal operating environment, then the receiver performance will degrade gracefully, causing a loss of navigation availability and/or continuity, but not a loss of integrity. This paper presents test results showing the performance of several GPS receivers under narrow-band (continuous wave) interference conditions. The parameters being monitored include position accuracy, code and carrier phase measurements, satellite geometry, carrier-to-noise ratio, and satellite lock time. This paper is of particular interest to: 1) GPS/WAAS/LAAS manufacturers whose sensors must meet the performance standards and 2) Aviation authorities responsible for both spectrum management and ground station/avionics development and certification.
Published in:	Proceedings of the 1996 National Technical Meeting of The Institute of Navigation January 22 - 24, 1996 Loews Santa Monica Hotel Santa Monica, CA
Pages:	765 - 778
Cite this article:	Skidmore, Trent, Liu, Fan, "GPS Interference: A Question of Inetgrity?," Proceedings of the 1996 National Technical Meeting of The Institute of Navigation, Santa Monica, CA, January 1996, pp. 765-778.
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