GNSS Receiver Tracking Loop Outage Handling
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Solution Overview
Problem
Global Navigation Satellite System (GNSS) receivers in wearable devices, such as watches, experience signal attenuation issues when submerged in water, leading to navigation solution errors due to alternating low and high signal levels, which can result in loss of track or large measurement errors.
Innovation Solution
Implementing a method where the tracking loops in the GNSS receiver can freewheel during short outages, allowing for rapid lock reacquisition upon signal restoration, and continuing to produce accurate position and velocity estimates using a numerically controlled oscillator, while opening or closing tracking loops based on signal level thresholds to manage signal attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tracking loops continue to track during water exposure, then the receiver maintains continuous tracking capability, but large measurement errors occur due to signal attenuation
Solution Approach 1:
The system performs preliminary actions by storing pre-computed satellite ephemeris data and orbital parameters before water exposure occurs. When signals are attenuated, the receiver can continue to compute accurate position solutions using this pre-loaded data without requiring real-time signal tracking, thereby maintaining reliability while avoiding measurement errors during submersion
Solution Approach 2:
The system cushions against signal attenuation by implementing a dual-mode tracking approach: during normal conditions, the receiver tracks signals continuously; when water exposure is detected or signal quality degrades, it transitions to using pre-computed orbital data. This beforehand preparation creates a protective buffer that prevents large measurement errors without requiring continuous tracking during adverse conditions
2Stability of the object's composition
If the navigation output rate is reduced to average solutions, then visually less jagged tracks are achieved, but position errors increase due to measurement delays
Solution Approach 1:
The system pre-computes satellite orbital parameters and ephemeris data at high rates before they are needed for navigation solutions. This preliminary computation allows the receiver to generate accurate position estimates without delaying measurements for averaging, as the computational work is already done in advance using pre-loaded satellite data
Solution Approach 2:
The system substitutes the mechanical approach of averaging multiple delayed measurements with a computational approach using pre-computed orbital mechanics data. By replacing the averaging process with direct computation from pre-loaded ephemeris and real-time signal data, the system achieves smooth tracks without the position errors that result from measurement delays
3Speed
If the tracking loops are opened during outages, then rapid lock reacquisition is enabled, but tracking loss occurs during the outage period
Solution Approach 1:
The system performs preliminary actions by maintaining and updating satellite orbital parameter data during outages when tracking loops are open. This pre-computed data is kept ready in memory, enabling rapid lock reacquisition as soon as signals return, while ensuring tracking availability is maintained through continuous data preparation during the outage period
Solution Approach 2:
The system ensures continuity of useful action by transitioning to a data preparation mode during outages rather than completely stopping operations. The receiver continues to process and update orbital parameters and ephemeris data even when tracking loops are open, ensuring that useful computational work continues without interruption and enabling seamless transition back to tracking mode
Data Source
AI summary
A system and a method are disclosed for handling outages in a Global Navigation Satellite System receiver. In some embodiments, the method includes: determining that a measure of combined signal level is less than a threshold, the measure of combined signal level being a measure of a signal level on a first channel of a Global Navigation Satellite System receiver and measure of a signal level on a second channel of the Global Navigation Satellite System receiver; and opening a tracking loop on a third channel of the Global Navigation Satellite System receiver.