GPS Receiver Almanac Correction for Fast TTFF
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Solution Overview
Problem
Current GPS receivers experience a slow Time to First Fix (TTFF) in weak-signal environments, which can take several minutes to provide a geographical location fix after being powered on, especially when using outdated ephemeris and almanac data.
Innovation Solution
The GPS receiver employs a demodulator to obtain ephemeris and almanac data, a calculator to calculate almanac correction parameters based on coordinate differences between ephemeris-based and almanac-based satellite positions, and a satellite positioning calculator to determine corrected satellite positions using updated data and parameters, thereby improving TTFF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional GPS receivers use standard ephemeris and almanac data processing, then the positioning process is simple, but the Time to First Fix (TTFF) is slow (several minutes) especially in weak-signal environments
Solution Approach 1:
The patent calculates and stores almanac correction parameters in advance using historical ephemeris and almanac data. These pre-computed correction parameters are then applied during the positioning process to accelerate satellite acquisition and improve TTFF, especially in weak-signal conditions. The preliminary calculation of correction parameters based on coordinate differences between ephemeris-based and almanac-based satellite positions enables faster convergence without requiring complex real-time computations.
2Productivity
If the GPS receiver uses outdated ephemeris and almanac data, then the device complexity is reduced, but the positioning accuracy and acquisition speed deteriorate
Solution Approach 1:
The patent employs a feedback mechanism where the receiver continuously compares ephemeris-based coordinates with almanac-based coordinates to calculate correction parameters. These corrections are fed back into the positioning system to adjust satellite position calculations. This feedback loop enables the system to maintain high acquisition efficiency and positioning precision by continuously refining satellite position data based on observed discrepancies between ephemeris and almanac models.
Data Source
AI summary
A GPS receiver includes a demodulator for obtaining ephemeris data and almanac data from a navigation message sent by satellites, and includes a calculator. The calculator is used for calculating almanac correction parameters according to coordinate differences between ephemeris-based coordinates of the satellites and almanac-based coordinates of the satellites. The GPS receiver also includes a satellite position calculator for calculating the ephemeris-based coordinates of the satellites according to the ephemeris data, for calculating the almanac-based coordinates of the satellites according to the almanac data, and for calculating positions of the satellites according to the ephemeris data, the almanac data and the almanac correction parameters.