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Detecting RFI Through Integrity Monitoring at a DGPS Reference Station

Published online by Cambridge University Press:  23 August 2006

Youngsun Yun ,
Changdon Kee ,
Jason Rife ,
Ming Luo ,
Sam Pullen  and
Per Enge
Youngsun Yun
Affiliation:
Seoul National University, Korea Email: zoro@snu.ac.kr
Changdon Kee
Affiliation:
Seoul National University, Korea Email: zoro@snu.ac.kr
Jason Rife
Affiliation:
Stanford University, USA
Ming Luo
Affiliation:
Stanford University, USA
Sam Pullen
Affiliation:
Stanford University, USA
Per Enge
Affiliation:
Stanford University, USA
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Abstract

Because GPS is a radio navigation system which has a very low power level, it is vulnerable to RFI. Excessive RFI could cause receiver performance degradation, such as degradation of position accuracy, loss of lock and increased acquisition time. 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 the Joint Precision Approach and Landing System (JPALS). This paper focuses on RFI mitigation through integrity monitoring for a 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 the 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 carrier-to-noise ratio (C/N0). Generating a monitoring threshold for these statistics proves challenging, because the threshold depends both on the type of RFI threat (e.g. 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.

Keywords

DGPSRadio Frequency InterferenceIntegrity Monitoring
Type
Research Article
Information
The Journal of Navigation , Volume 59 , Issue 3 , September 2006 , pp. 403 - 422
Copyright
Copyright © The Royal Institute of Navigation 2006

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References

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