Virtual Beacon GNSS Integrity Check Using MAC Bias Compensation
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Solution Overview
Problem
Existing GNSS positioning systems face challenges in ensuring the integrity and accuracy of location measurements, particularly in environments with signal masking or satellite failure, leading to potential position errors that exceed safety requirements for applications like rail traffic, due to synchronization errors, propagation disturbances, and interference.
Innovation Solution
A method using Generalized Spatial Correlation (GSC) combined with a 'Maximum At Center' (MAC) integrity check to verify the consistency of received GNSS signals with predefined reference positions, adjusting for synchronization and propagation errors, and excluding biased signals to define a protective radius.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard GNSS positioning algorithm is used, then positioning is achieved, but the integrity and accuracy of location measurements cannot be ensured in environments with signal masking, satellite failures, and interference
Solution Approach 1:
The patent performs preliminary integrity checks by comparing the correlation function of received GNSS signals with correlation functions of signals expected at predefined reference positions before finalizing the position determination. This preliminary verification ensures that only signals consistent with expected propagation characteristics are used, preventing position errors caused by signal masking, satellite failures, and interference.
Solution Approach 2:
The patent implements a feedback mechanism where the integrity of the position determination is continuously monitored by comparing actual signal correlation characteristics with expected values at reference positions. This feedback loop allows the system to detect and reject erroneous signals or position solutions that do not meet integrity thresholds, thereby ensuring both reliability and precision.
2Measurement precision
If the protection radius is reduced to improve measurement precision, then the number of false alarms increases and availability decreases
Solution Approach 1:
The patent dynamically adjusts the protection radius parameter based on the quality of signal correlation and the confidence level of position determination. By changing this parameter adaptively rather than using a fixed value, the system maintains high precision when signal quality is good while increasing availability when signal conditions are marginal, thus avoiding excessive false alarms without compromising precision.
Data Source
AI summary
A method for checking the integrity of the point positioning process obtained by determining the closest position, based on the adapted filtering of received GNSS signals, of a set of georeferenced reference positions for implementation on a mobile or fixed carrier, the method making it possible to check that the correlation function of the received GNSS signals is consistent with the selected reference position. The method for checking the integrity of the nearest location comprises: a first step for pre-selecting satellite signals suitable for the position integrity test, based on the minimum signal-to-noise ratio of the point correlation channel, a second step to exclude satellite signals that are not compatible with the predicted code phases, based on the absence of a Maximum At Center (MAC) of the early-punctual-late correlation points and meeting the non-integrity, non-continuity and alarm delay risks required for positioning system security, at least one maximum likelihood search step on the set of reference positions obtained by cumulating the elementary powers of the various selected satellites.