GNSS Satellite Line of Sight Classification via Doppler Vector Analysis
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Solution Overview
Problem
Global navigation satellite systems (GNSS) face accuracy issues in urban areas due to blocked lines of sight from terrestrial objects, requiring a method to differentiate between line-of-sight (LOS) and non-line-of-sight (NLOS) satellites to improve position calculation accuracy.
Innovation Solution
A method and device that classify GNSS satellites as LOS or NLOS by computing relative and Doppler vectors from received signals and ephemeris data, comparing these vectors to determine the satellite's visibility status, using either two timestamps or frequent ephemeris data extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GNSS receiver operates in urban areas with tall buildings, then the receiver can still receive signals from satellites, but the line of sight to satellites is blocked by obstacles forming urban canyon
Solution Approach 1:
The patent segments the satellite signal reception problem by classifying each satellite as either LOS (line-of-sight) or NLOS (non-line-of-sight) based on signal characteristics. This segmentation allows the system to handle different signal types differently, improving overall position determination accuracy in urban environments where mixed LOS and NLOS conditions exist.
Solution Approach 2:
The patent changes the parameter analysis by examining multiple signal characteristics including Doppler shift, signal strength, and arrival time to determine satellite classification. By analyzing these parameters and comparing them against expected LOS values, the system can identify NLOS satellites and exclude them from position calculations, thereby resolving the contradiction between signal availability and position accuracy.
2Measurement precision
If at least four LOS satellites are required for accurate position determination, then position accuracy is improved, but the number of usable satellites decreases in obstructed environments
Solution Approach 1:
The patent introduces an intermediary classification mechanism that acts as a mediator between signal reception and position determination. By classifying satellites as LOS or NLOS based on signal characteristics, the system can selectively use only LOS satellites for position calculation, ensuring accuracy while maximizing the number of usable satellites in obstructed environments.
Solution Approach 2:
The patent implements feedback by continuously monitoring signal characteristics and adjusting satellite classification accordingly. The system uses Doppler shift measurements and signal strength analysis to provide feedback on satellite status, allowing dynamic adjustment of which satellites are used for position determination, thus maintaining accuracy while optimizing satellite utilization.
3Measurement precision
If Doppler vector and relative direction vector are computed and compared, then satellite classification accuracy is improved, but the computational complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-computing expected Doppler shift values based on satellite ephemeris data and receiver position. This preliminary calculation allows for faster comparison with actual measured Doppler shifts, reducing real-time computational complexity while maintaining classification accuracy. The system prepares reference vectors in advance, so only simple comparisons are needed during operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances the accuracy of GNSS position calculations by distinguishing between satellites with and without a clear line of sight, improving positioning in obstructed environments.
Implementation Method 1
computing a Doppler vector indicating the direction of motion of the GNSS receiver relative to the GNSS satellite, based on Doppler shifts computed for each of the received signals
Data Source
AI summary
The invention, in some embodiments, relates to the field of global navigation satellite systems, and more particularly to the field of methods and devices for identifying whether a satellite in a global navigation satellite system has a line of sight to a specific global navigation satellite system receiver (LOS satellite) or does not have a line of sight to the global navigation satellite system receiver (NLOS satellite).