GNSS Receiver Time Error Detection Using CNo Deltas
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Solution Overview
Problem
GNSS receivers experience time errors due to erroneous time uncertainty (TUNC) values, leading to undesirable conditions such as long time periods without a fix, incorrect position fixes, and erroneous pulse per second signals, which are difficult to detect and correct.
Innovation Solution
The method involves determining a carrier-to-noise (CNo) delta between different types of GNSS signals to detect time errors and performing error mitigation operations, such as selecting a GNSS signal with lower susceptibility to errors and using threshold CNo deltas for accurate time error detection and correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the GNSS receiver uses erroneous time uncertainty (TUNC) values to skip acquisition steps and reduce TTFF, then the time to first fix is reduced, but time errors occur leading to incorrect position fixes and erroneous pulse per second signals
Solution Approach 1:
The system continuously monitors the relationship between CNo values of different GNSS signals and compares it against expected thresholds. When the CNo difference exceeds the threshold, it indicates a time error condition, triggering feedback mechanisms to detect and mitigate the error while maintaining fast acquisition capabilities
Solution Approach 2:
The patent introduces CNo (carrier-to-noise ratio) as an intermediary parameter to indirectly detect time errors. Instead of directly measuring time uncertainty, the system uses CNo differences between signal types as a mediator to infer the presence of time errors, enabling reliable detection without compromising acquisition speed
2Measurement precision
If the GNSS receiver performs complete acquisition procedures for all signal types, then positioning accuracy is maintained, but time to first fix increases and productivity decreases
Solution Approach 1:
The system performs preliminary CNo ratio calculations and threshold comparisons during the acquisition process itself, rather than requiring separate verification steps. This preliminary action enables the system to quickly identify and mitigate time errors without delaying the acquisition procedure, maintaining both speed and accuracy
Solution Approach 2:
The acquisition procedure is made dynamic by allowing the system to adapt its behavior based on real-time CNo monitoring. When time errors are detected through CNo threshold violations, the system dynamically adjusts its acquisition strategy to mitigate errors while maintaining progress, rather than following a static fixed procedure
3Device complexity
If the GNSS receiver uses single-frequency signals for acquisition, then device complexity is reduced, but susceptibility to time errors increases and reliability decreases
Solution Approach 1:
The patent makes the CNo monitoring mechanism universal by applying the same threshold-based detection approach across different GNSS signal types and frequencies. This multi-functional approach allows the system to maintain simple single-frequency acquisition while using the universal CNo comparison method to detect time errors in any signal type, improving reliability without increasing complexity
Data Source
AI summary
A method to detect time errors in a global navigation satellite system (GNSS) receiver can include determining a carrier-to-noise (CNo) delta between a CNo ratio of a first type of GNSS signal and a CNo ratio of a second type of GNSS signal. A time error may be detected based on the first CNo delta and a first threshold CNo delta, the time error indicating a use of an erroneous time uncertainty (TUNC) by the GNSS receiver. An error mitigation operation may be performed based on detecting the time error. The first type of GNSS signal may be selected based on determining that a first level of susceptibility to errors associated with the first type of GNSS signal is lower than a second level of susceptibility to errors associated with the second type of GNSS signal.