GNSS RFI Sigma Averaging for Faster Satellite Readmittance
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Solution Overview
Problem
Global navigation satellite system (GNSS) receivers experience accuracy issues due to broadband radio frequency interference (RFI), leading to exclusion of satellite measurements from differential correction data and integrity monitoring, requiring a method to quickly and reliably readmit these measurements when interference decreases.
Innovation Solution
A method involving the calculation of first and second RFI-based averaged sigmas, where the first sigma includes the excluded measurement and the second sigma does not, allowing readmission when the first sigma is less than or equal to the second, facilitating quicker reacceptance into differential corrections and integrity monitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If satellite measurements are excluded from differential correction data and integrity monitors when C/N0 drops below threshold due to RFI, then measurement reliability is improved, but system productivity and positional accuracy deteriorate due to loss of available measurements
Solution Approach 1:
The patent implements dynamic readmittance criteria that adapt to current signal conditions. Instead of permanently excluding satellite measurements when C/N0 drops below threshold, the system continuously monitors signal quality and allows readmittance when conditions improve, creating a dynamic rather than static exclusion approach that optimizes both reliability and productivity
Solution Approach 2:
The system employs feedback mechanisms by continuously monitoring C/N0 values and using this information to control the readmittance decision process. The readmittance criteria are based on feedback from signal quality measurements, allowing the system to adjust its behavior based on current RFI conditions and restore measurements when appropriate
2Reliability
If satellite measurements are excluded during RFI events, then integrity monitor reliability is improved, but time loss and system downtime increase
Solution Approach 1:
The patent establishes predetermined readmittance criteria before RFI events occur. These criteria, based on C/N0 thresholds and signal quality metrics, are prepared in advance to enable rapid readmittance decisions when interference subsides, reducing the time loss associated with reevaluating readmittance conditions after an event
3Productivity
If excluded satellite measurements are quickly readmitted when C/N0 improves, then system availability is improved, but risk of reaccepting corrupted measurements increases
Solution Approach 1:
The system uses continuous feedback from C/N0 monitoring to control the readmittance process. Rather than immediately readmitting measurements when C/N0 first exceeds the threshold, the system uses the feedback signal to verify sustained improvement in signal quality, ensuring that readings are not reaccepted during ongoing interference events
Solution Approach 2:
The patent introduces an intermediary readmittance evaluation process between the exclusion decision and the actual readmittance of measurements. This intermediary step evaluates multiple criteria including C/N0 thresholds and signal stability to mediate the transition from excluded to accepted status, preventing premature readmittance of corrupted data
Data Source
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AI summary
Systems and methods for averaging satellite sigmas and readmitting excluded satellite measurements into differential corrections and integrity monitors are provided. In one embodiment, a method comprises: calculating a first RFI based averaged sigma and a second RFI based averaged sigma, wherein the first RFI based averaged sigma includes a sigma for the excluded satellite measurement and wherein the second RFI based averaged sigma does not include the sigma for the excluded satellite measurement; and, readmitting the excluded satellite measurement into either a differential correction broadcast or a respective integrity monitor when the first RFI based averaged sigma is less than or equal to the second RFI based averaged sigma.