GNSS Localization via Reflected Signal Doppler Shifts
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Solution Overview
Problem
GNSS receivers in urban environments face inaccuracies due to signal reflections, leading to 'wrong-side-of-the-street' issues, as existing methods like inertial systems and shadow matching are ineffective or oversimplify the problem, and correcting excess path length is challenging without an accurate initial location.
Innovation Solution
The method utilizes Doppler shifts of reflected signals by generating candidate positions around an estimated receiver location, determining predicted Doppler effects through ray-tracing, and identifying the actual location by matching measured Doppler effects, allowing for accurate positioning and speed determination without relying on signal strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional GNSS localization methods are used in urban environments, then the system is simple to operate, but the positioning accuracy deteriorates due to signal reflections causing 'wrong-side-of-the-street' issues
Solution Approach 1:
The patent segments the search space into multiple candidate positions around the estimated receiver location. Instead of treating localization as a single-point determination, the system divides the area into discrete candidate positions and evaluates each one independently using ray-tracing and Doppler effect comparison, thereby improving accuracy through systematic exploration of possible locations
Solution Approach 2:
The patent performs preliminary ray-tracing calculations and Doppler effect predictions for multiple candidate positions before making the final location determination. By pre-computing the expected Doppler effects at each candidate position based on reflected signal paths, the system prepares all necessary data in advance to accurately identify the actual receiver location
Solution Approach 3:
The patent changes the approach from using signal strength parameters to using Doppler effect parameters for location determination. By measuring and comparing Doppler shifts caused by reflected signals at different candidate positions, the system transforms the localization problem into a parameter-matching exercise that is more robust to signal reflections
2Measurement precision
If inertial systems or shadow matching methods are used to correct locational inaccuracies, then positioning accuracy may improve, but the device complexity increases and these methods are ineffective in dense urban environments
Solution Approach 1:
The patent makes the GNSS receiver self-sufficient by using its own received signals (including reflected signals) to determine its location. The system processes the Doppler effects of signals already present in the environment without requiring additional sensors, external infrastructure, or complex inertial measurement units, thereby improving accuracy while avoiding increased device complexity
Solution Approach 2:
The patent replaces mechanical/inertial systems with a signal-processing approach based on electromagnetic wave properties. Instead of using accelerometers, gyroscopes, or shadow matching algorithms, the system uses Doppler effect analysis of reflected GNSS signals, substituting a purely electronic solution for mechanical or geometric methods that fail in dense urban environments
3Measurement precision
If additional hardware is added to improve positioning accuracy in urban environments, then measurement precision improves, but the ease of operation deteriorates due to calibration and setup requirements
Solution Approach 1:
The patent makes the existing GNSS receiver multi-functional by enabling it to perform both standard localization and Doppler-based reflected signal analysis using the same hardware components. The antenna and signal processor that normally receive direct satellite signals are also used to detect and analyze reflected signals, eliminating the need for additional specialized hardware while maintaining ease of 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
This approach effectively corrects locational inaccuracies in urban environments by accurately identifying the GNSS receiver's position and speed, even with signal attenuation, and does not require initial direct signals or additional hardware, improving positioning accuracy and reliability.
Implementation Method 1
receiving a measured Doppler effect for a GNSS signal from the respective available satellite caused by the moving GNSS receiver
Implementation Method 2
Localization using doppler shifts of reflected signals
Data Source
AI summary
A method of Doppler-based localization includes establishing an estimated position for a moving receiver. The method also includes generating a plurality of candidate positions about the estimated position. Each candidate position corresponds to a possible actual location of the moving receiver. For each available satellite, the method includes receiving a measured Doppler effect for a signal from the respective available satellite caused by the moving receiver. For each available satellite, the method also includes, at each candidate position, determining a predicted direction of the signal based on ray-launching the signal to the respective satellite and generating a predicted Doppler effect for the moving receiver. The method further includes identifying a respective candidate position as an actual location for the moving receiver when, at the respective candidate position, the predicted Doppler effect for at least one satellite most closely matches the measured Doppler effect for the at least one satellite.