RAIM Algorithm Integrity Risk Segmentation
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Solution Overview
Problem
Current RAIM algorithms for GNSS receivers lack sufficient confidence in calculating integrity risks, particularly failing to achieve the stringent requirements of 1E-7 integrity risk confidence, as they rely on statistical descriptions with lower confidence levels.
Innovation Solution
The algorithm determines a subgroup of 'fault-free' ranging signals and calculates integrity risk by removing potentially faulty signals from this subgroup, using redundancy to enhance confidence, thereby increasing the reliability of integrity risk determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If statistical descriptions with confidence level 1-1E-4 are used for integrity risk calculation, then the calculation can be performed with available data, but the confidence in integrity risk determination is insufficient to achieve 1E-7 integrity risk requirements
Solution Approach 1:
The patent segments the set of fault-free ranging signals into multiple subgroups. Each subgroup is used to calculate a separate integrity risk value. The final integrity risk is determined as the maximum of these calculated values. This segmentation allows the system to achieve higher confidence (1E-7) by distributing the statistical uncertainty across multiple independent calculations rather than relying on a single calculation with lower confidence (1E-4).
Solution Approach 2:
The patent performs more integrity risk calculations than the minimum single calculation would provide. By calculating integrity risks for multiple subgroups and taking the maximum, the system performs excessive action (multiple calculations) to ensure the final result meets the stringent 1E-7 confidence requirement, exceeding what a single calculation could achieve.
2Reliability
If all fault-free ranging signals are used for integrity risk determination, then the calculation utilizes available redundancy, but the confidence remains insufficient because at least two signals could be statistically incorrect
Solution Approach 1:
The patent divides the complete set of fault-free ranging signals into multiple smaller subgroups. This segmentation ensures that not all signals are dependent on the same statistical assumptions, reducing the risk that multiple signals share the same statistical error. The algorithm complexity increases moderately due to multiple calculations, but this is justified by the significant improvement in confidence from 1E-4 to 1E-7.
Solution Approach 2:
The patent changes the parameter of statistical confidence by performing multiple integrity risk calculations with different signal subgroups. Each calculation uses the same mathematical framework but different input subsets, effectively changing the statistical parameters (which specific signals are included) to achieve higher overall confidence in the final integrity risk determination.
3Reliability
If a subgroup of fault-free ranging signals is used instead of all signals, then confidence in integrity risk determination increases, but the quantity of signals used for calculation decreases
Solution Approach 1:
The patent segments the full set of available ranging signals into multiple subgroups for calculation. While each individual subgroup contains fewer signals than the total set, the overall reliability increases because the segmentation strategy ensures that statistical errors in one subgroup do not systematically affect all calculations. The final integrity risk is derived from the maximum of multiple subgroup-based calculations.
Solution Approach 2:
The patent extracts specific subgroups of ranging signals from the complete set of fault-free signals. By selectively extracting and using only certain subgroups for each integrity risk calculation, the system achieves higher confidence levels. The extraction process deliberately limits the number of signals in each subgroup to ensure statistical independence and reduce the probability of multiple signals sharing the same statistical error.
Data Source
Figure 1
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AI summary
The invention relates to a RAIM algorithm for determining an integrity risk in a GNSS by processing several ranging signals received from satellites of the GNSS wherein the algorithm comprises the following acts: determining a first group of ranging signals from received ranging signals for determining the integrity risk (S10), wherein a statistical description of each ranging signal of the first group determines the ranging signals as being fault-free, selecting from the first group of ranging signals at least one ranging signal assuming that the statistical description of this ranging signal is not correct (S12), determining a second group of ranging signals from the first group by removing the selected at least one ranging signal from the first group of ranging signals (S14), and determining the integrity risk as the maximum of the integrity risks of all possibilities calculated from the second group of ranging signals at the alert limit (S16).