A-GNSS Server Time Error Detection and Compensation
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Solution Overview
Problem
Conventional assisted Global Navigation Satellite System (A-GNSS) technologies face inaccuracies in determining the geographic location of mobile devices due to erroneous time measurements, which are not corrected by the system, leading to position errors and reduced yield.
Innovation Solution
A method is implemented where a server-based A-GNSS system detects erroneous time measurements and substitutes a recovered time for accurate position calculation, using a communication interface and processor to request and process measurement information from a GNSS receiver, determining the accuracy of the measured time and employing a substitute time when necessary to ensure accurate position determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the system uses measured time from the mobile device for position calculation, then the position determination can be performed with fewer measurements (4 satellites), but erroneous time measurements cause large position errors and reduced yield
Solution Approach 1:
The system performs preliminary time error detection by comparing the measured time against an expected time range before initiating position calculation. This preliminary check allows the system to identify erroneous time measurements in advance, preventing wasted computational resources and enabling timely recovery actions such as requesting additional satellite measurements or using alternative time sources.
Solution Approach 2:
The system implements a feedback mechanism where the measured time is validated against expected parameters, and when errors are detected, the system responds by adjusting the calculation approach (e.g., using 5th satellite measurement for time recovery). This closed-loop feedback ensures that position determination continues with high accuracy even when initial time measurements are erroneous.
2Measurement precision
If the system requires accurate measurement time for position calculation, then position accuracy is maintained, but erroneous time measurements outside the accurate time range cannot be corrected
Solution Approach 1:
The system establishes an accurate time range as a buffer zone before performing position calculations. By defining this acceptable time window in advance based on the first and second times, the system creates a safety margin that accommodates small timing variations while clearly identifying when time errors are too large to correct, thus preventing unreliable calculations.
Solution Approach 2:
When the measured time falls outside the accurate time range, the system changes the calculation parameters by incorporating a fifth satellite measurement to recover the measurement time. This parameter change transforms the problem from an unsolvable state (erroneous time) to a solvable state (recovered time through additional measurements).
3Productivity
If the MLC recovers measurement time from inaccurate input, then position calculation can proceed, but an approximate time accurate within a certain window is necessary to initiate the process
Solution Approach 1:
The system performs preliminary validation of the measured time against the accurate time range before attempting time recovery. This preliminary action ensures that only measurements with sufficient approximate accuracy (within the acceptable window) are processed further, preventing wasted computational effort on completely erroneous measurements while maintaining high productivity for valid inputs.
Data Source
AI summary
A method implemented by an assisted Global Navigation Satellite System (GNSS) server determines a position of a GNSS receiver. The method includes sending a request for measurement information to the GNSS receiver at a first time and receiving the measurement information from the GNSS receiver in response to the request at a second time, where the measurement information includes position measurement data and a corresponding measured time based on satellite signals received by the GNSS receiver. The measured time is determined to be erroneous when it is outside an accurate time range determined based on at least one of the first time and the second time. A substitute time is identified and the position of the GNSS receiver is determined based on the substitute time when the measured time is erroneous.