GNSS Clock Frequency Spoof Detection Using a Wiener Process
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Solution Overview
Problem
Existing GNSS equipment struggles to effectively detect and exclude spoofing signals, which introduce common-mode errors affecting clock bias and frequency estimates, compromising position, velocity, and time calculations crucial for safety and mission effectiveness.
Innovation Solution
Adapting a Wiener process disorder detector within GNSS receivers to identify deviations in clock frequency estimates, utilizing Kalman filtering to model expected behavior and detect spoofing by comparing observed behavior to expected Wiener process models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Kalman filtering is used to estimate PVT, then position and velocity estimates are obtained, but the system becomes vulnerable to spoofing signals that introduce common-mode errors
Solution Approach 1:
The patent introduces an intermediary detection mechanism (disorder detector) that monitors the clock frequency estimates separately from the main PVT estimation process. This intermediary system analyzes the statistical properties of clock estimates to detect spoofing without directly interfering with the Kalman filtering PVT calculations, thus maintaining measurement precision while improving reliability.
Solution Approach 2:
The patent segments the fault detection function into a separate disorder detector module that operates independently from the main Kalman filter. This segmentation allows the system to maintain accurate PVT estimates through the filter while simultaneously monitoring for spoofing through the separate disorder detection process, resolving the contradiction between precision and reliability.
2Reliability
If fault detection algorithms are added to GNSS equipment, then spoofing detection capability is improved, but device complexity increases
Solution Approach 1:
The disorder detector leverages existing clock frequency estimates that are already computed as part of the standard Kalman filtering process for PVT estimation. Rather than requiring completely separate measurement systems, the patent makes the existing clock estimates serve a dual purpose: maintaining time synchronization and detecting spoofing through statistical analysis, thus improving reliability without proportionally increasing complexity.
Solution Approach 2:
The patent makes the clock frequency estimates serve multiple functions: they are used both for standard time synchronization in the Kalman filter and for spoofing detection in the disorder detector. This multi-functionality allows the system to gain spoofing detection capability without adding completely separate measurement hardware or processing paths, thereby limiting the increase in device complexity.
Data Source
AI summary
An apparatus that performs spoof detection of satellite signals based on clock information derived from the satellite signals. The apparatus may include a position, velocity, time (PVT) component that derives the clock information from the satellite signals and provides the clock information to a spoof detection mechanism. In some embodiments, the clock frequency estimate is modeled as a Wiener process.