A Survey of Possible Methods for Mitigating the Impact of Radio Frequency Interference on Satellite Navigation Systems Used for Precision Approach

摘要

A notable feature of the Global Positioning System (GPS) and its sister Global Navigation Satellite Systems (GNSS) is their susceptibility to radio frequency interference (RFI). The power level of a GNSS signal received near the Earth's surface is orders of magnitude below ambient noise levels. As a result, GPS users are vulnerable to disruption or loss of the satellite navigation capability. The majority of disruptions are unintentional, although much work needs to be done to mitigate their impact on GPS. In addition, GPS disruption technology is fairly mature at this time, so that considerable harm can be caused to civil aviation if would-be perpetrators see a benefit to doing so. Although unintentional and intentional RFI is and to some degree will remain a threat to satellite navigation, much can be done to develop safe, economic and effective systems by mitigating or even eliminating the worst RFI threats. The FAA is designing a GPS-based precision approach system, the Local Area Augmentation System (LAAS)-see Figure 1. A major challenge to implementing this system is dealing successfully with RFI and multipath disruptions. This paper will survey the nature, sources and impacts of the likely RFI threats to safe and reliable use of LAAS, focusing on Category II and III precision approach operations. It also will survey the various RFI mitigation practices and design options applicable to LAAS.