The Federal Aviation Administration (FAA) Wide AreaAugmentation System (WAAS) Monitoring Team hasinvestigated increases in Radio Frequency Interference(RFI) events observed since 2009. The Oklahoma CitybasedWAAS Monitoring Team initially observed increasedRFI events at certain WAAS Reference Stations(WRSs). The major source for this increase in RFI eventshas been attributed to Global Positioning System (GPS)maskers used in motor vehicles for personal privacy. Theuse of these Personal Privacy Devices (PPDs) is observedin WRS operation via a response in the Automatic GainControl (AGC) and the signal to noise ratio (C/N0) reportedby the reference receivers. More importantly, the PPDscan occasionally cause the WAAS receivers to lose trackingon some GPS or WAAS Geostationary Earth Orbit(GEO) satellites. To date, there have been no WAAS servicedegradations attributed to these PPD events. Thispaper will analyze what the WAAS Monitoring Team hasobserved from these PPD events and will review the investigationactivities that took place at the WRSs nearChicago, Houston, Boston and Washington, DC. The paperwill present the results of a spatial analysis study toassess the risk to WRSs posed by PPDs based on theirlocation relative to nearby roads. It will also review asimulation of the effect of increased PPD usage onWAAS service. Lastly, it will discuss the next steps forhow WAAS will respond to the inevitable presence andoperation of PPDs around reference stations.
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