Detecting RFI Through Integrity Monitoring at a DGPS Reference Station

Youngsun Yun, Changdon Kee, Jason Rife, Ming Luo, Sam Pullen, Per Enge

Abstract:	"Because GPS is a radio navigation system which has a very low power level, it is vulnerable to RFI (Radio Frequency Interference). Excessive RFI could cause degradation of position accuracy, loss of lock, increased acquisition time, etc. After GPS modernization plans introduce dual-frequency civil signals to mitigate ionospheric errors, RFI will remain as one of the dominant threats for differential GPS navigation systems. Examples of safety-critical civil aviation and military missions threatened by RFI include the Local Area Augmentation System (LAAS) and Joint Precision Approach and Landing System (JPALS). This paper focuses on RFI mitigation through integrity monitoring for a Differential GPS (DGPS) system like LAAS or JPALS. The mitigation strategy consists of two parts. First, the paper develops a new RFI detection method, using a raw divergence statistic. Second, the paper investigates strategies for maintaining integrity in case that RFI is detected. To validate the utility of the divergence-based RFI monitor, this paper takes an experimental approach. The experiments assess the performance of the divergence metric and compare it to existing alternatives for RFI detection, such as metrics for Automatic Gain Control (AGC) and signal-to-noise (C/N0). Generating a monitoring threshold for these statistics proves challenging, because the threshold depends both on the type of RFI threat (continuous wave, narrow band, wideband, pulsed) and on environmental conditions, such as temperature. As experiments illustrate, the divergence statistic resolves these limitations, as divergence directly estimates ranging source error, independent of the type of RFI threat or the environmental conditions."
Published in:	Proceedings of the 61st Annual Meeting of The Institute of Navigation (2005) June 27 - 29, 2005 Royal Sonesta Hotel Cambridge, MA
Pages:	795 - 804
Cite this article:	Yun, Youngsun, Kee, Changdon, Rife, Jason, Luo, Ming, Pullen, Sam, Enge, Per, "Detecting RFI Through Integrity Monitoring at a DGPS Reference Station," Proceedings of the 61st Annual Meeting of The Institute of Navigation (2005), Cambridge, MA, June 2005, pp. 795-804.
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