GNSS Navigation Fix Verification via Residual Analysis
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Solution Overview
Problem
Existing Global Navigation Satellite Systems (GNSS) face challenges in verifying navigation solutions that use both signals with trusted data and signals with no trusted data, as the inclusion of unauthenticated signals can lead to incorrect or false position fixes due to spoofing attacks.
Innovation Solution
A method is introduced to generate a navigation solution using all available signals and calculate the difference between the solution and the pseudo-range for each signal, known as the residual. By analyzing the distribution of residuals from trusted and untrusted signals, the authenticity of the untrusted signals can be determined, allowing for verification of the navigation solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signals without trusted data are included in the navigation solution, then the accuracy of the position fix is improved, but the reliability of the navigation solution deteriorates due to potential spoofing attacks
Solution Approach 1:
The patent segments the residual values into two distinct groups: residuals from signals with trusted data and residuals from signals without trusted data. This segmentation allows for separate statistical analysis of each group, enabling the system to identify and isolate potential spoofed signals while maintaining the benefits of using all available signals for the navigation solution.
Solution Approach 2:
Instead of trying to directly authenticate signals without trusted data, the patent inverts the approach by analyzing what the residuals should look like if the signals were legitimate. By comparing the actual residuals against expected statistical characteristics, the system can identify anomalies that indicate spoofing, thereby verifying authenticity through negative evidence.
2Reliability
If only signals with authenticated data are used, then the reliability of the navigation solution is improved, but the measurement precision deteriorates due to reduced signal availability
Solution Approach 1:
The patent implements a feedback mechanism where the statistical characteristics of residuals from trusted signals are continuously monitored and used to establish expected patterns. These patterns then serve as a reference for evaluating signals without trusted data, creating a feedback loop that enables reliable verification while maintaining high measurement precision through full signal utilization.
3Reliability
If statistical analysis of residuals is performed to verify signal authenticity, then the reliability of the navigation solution is improved, but the device complexity increases
Solution Approach 1:
The patent applies the self-service principle by having the system use its own residual data from trusted signals to automatically establish verification criteria and evaluate untrusted signals. The system serves itself by generating the statistical benchmarks from its own operational data, eliminating the need for external verification infrastructure or complex pre-configured authentication parameters.
Data Source
AI summary
According to the invention there is provided a method of determining verification of a PVT solution in a global navigation satellite system, GNSS system, receiver, the method comprising receiving a plurality of GNSS signals from a plurality of satellites, a first plurality of the signals having no trusted data and a second plurality of the signals having trusted data; estimating a PVT solution based on all the received GNSS signals; determining, for each received signal, a residual comprising the difference between the range of the space vehicle to the estimated PVT solution and a the pseudo-range of each signal; determining a statistic from the residuals of the first plurality of signals; comparing the statistic to a first value; and, responsive to the comparison, determining the position to be verified or not to be verified.