GIDL: Generalized Interference Detection and Localization System

Konstantin Gromov, Dennis Akos, Sam Pullen, Per Enge and Bradford Parkinson

Abstract:	The Local Area Augmentation System (LAAS) and the Wide Area Augmentation System (WAAS) are being developed by the U.S. Federal Aviation Administration (FAA) to provide satellite navigation performance compliant with the stringent requirements for aircraft precision approach and landing. A primary design goal of both systems is to insure that signal-in-space failures are detected by ground facilities and affected measurements are excluded before differential corrections are broadcast to users. One such failure is unintentional interference or intentional jamming in the GPS frequency band. To protect integrity, LAAS and WAAS ground facilities must quickly detect the presence of interference that fall within the restricted zone de- fined by LAAS and WAAS system requirements and thus may be hazardous to users. To protect availability, ground personnel must also be able to locate and deactivate the interference source. To serve this purpose, Stanford University developed and tested a 1-D Interference Direction Finding system and reported its results at ION GPS-99. This prototype demonstrated the ability to locate wideband interference sources to within a few centimeters along a 12-meter track between the two IDF antennas. This system has been significantly expanded and enhanced to form the Generalized Interference Detection and Localization System (GIDL) prototype, which includes four antennas and RF sections slaved to a common clock to allow three-dimensional interference location. Measurements of differential signal propagation delays across the multiple baselines between the GIDL antennas are combined to estimate the location of the undesired signal transmitter in a manner analogous to GPS position determination. The GIDL can be implemented in parallel with a three or four-receiver LAAS ground facility (sharing some components with the LAAS reference receivers and processors) or as a separate installation to support nearby LAAS sites and WAAS approaches. This paper describes the GIDL receiver design and derives theoretical predictions of the ability of the GIDL to accurately locate interference sources. For the “star” configuration of GIDL antennas, where the antennas are separated by 100 meters (as would be typical of a LAAS ground facility), the GIDL should be able to locate a relatively strong interference source 3 km from the center of the GIDL antennas to within 100 meters longitudinally and 5 meters laterally. Better accuracy can be obtained from longer antenna separations. In addition, the paper includes test results from a real-time demonstration of the GIDL system in a large field on the Stanford campus. In this test, a calibrated wideband noise source at -70 dBW/MHz is moved around the field between a set of pre-calibrated locations, and the realtime GIDL display provides up-to-date estimates of the location of this noise source to within the limits predicted by the accuracy analysis. Further testing with a wider variety of interference sources is planned in the near future.
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	447 - 457
Cite this article:	Gromov, Konstantin, Akos, Dennis, Pullen, Sam, Enge, Per, Parkinson, Bradford, "GIDL: Generalized Interference Detection and Localization System," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 447-457.
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