GNSS Receiver Correlation Mapping for Urban Multipath Detection
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Solution Overview
Problem
Conventional Global Navigation Satellite System (GNSS) receivers struggle to accurately distinguish line of sight (LOS) signals from multipath (NLOS) signals in urban canyon areas, leading to reduced accuracy in position and velocity estimation due to interference and overlap, as existing methods relying on signal amplitude are unreliable.
Innovation Solution
A method and system that processes positioning signals using a frequency generator, code generator, and correlator to generate correlation maps, identifying LOS and multipath correlation peaks, and employs feedback information to refine clock bias estimates, allowing for accurate position and velocity determination without requiring highly stable oscillators or IMUs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional receiver systems use signal amplitude to identify LOS signals, then the system is simple to operate, but the measurement precision of position and velocity estimation deteriorates due to unreliable distinction between LOS and multipath signals
Solution Approach 1:
The patent segments the correlation peaks into distinct categories (LOS correlation peaks and multipath correlation peaks) based on their characteristics in the correlation map. By separating these peaks into different groups, the system can process and estimate clock bias using only the identified LOS peaks, thereby improving measurement precision while managing complexity through systematic organization of signal components
Solution Approach 2:
The patent transitions from one-dimensional signal amplitude comparison to two-dimensional analysis by examining both code phase delay and Doppler frequency characteristics in the correlation map. This dimensional expansion allows the system to distinguish LOS signals from multipath signals more reliably, as the additional dimension provides extra discrimination capability beyond what amplitude alone can provide
2Measurement precision
If the receiver system uses multiple measurement periods with feedback to refine clock bias estimates, then the measurement precision improves, but the loss of time increases due to extended processing duration
Solution Approach 1:
The patent performs preliminary identification of LOS correlation peaks and estimation of clock bias in the first measurement period, then uses these results as feedback to guide the processing in subsequent measurement periods. This preliminary action reduces the need for extensive search and analysis in later periods, as the system can focus only on refining the estimates using the identified peaks, thereby improving precision while limiting time loss
Solution Approach 2:
The patent implements a feedback mechanism where the clock bias estimate from one measurement period is used as input for the next measurement period. This feedback loop allows the system to progressively refine its clock bias estimation using multiple periods without requiring each period to be independently exhaustive, as the feedback from previous periods guides and constrains the current period's processing
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 position and velocity estimation in urban canyon environments by effectively distinguishing LOS signals from multipath signals, reducing inaccuracies and maintaining cost-effectiveness.
Implementation Method 1
a correlator configured to receive the local carrier signal, the local code signal, and a signal generated using the positioning signals, and generate a correlation signal indicative of a correlation between the received positioning signals and the local carrier signal, and a correlation between the received positioning signals and the code signal
Implementation Method 2
determining a LOS code phase delay and a LOS Doppler frequency for the second measurement period
Data Source
AI summary
A satellite navigation system comprises a receiver system configured to receive positioning signals from one or more satellites and generate positon, velocity, and calibration data using the positioning signals. The calibration data may include information about multipath positioning signals identified during different measurement periods associated with a reference trajectory. The receiver system generates the positon, velocity, and calibration data for a measurement period based on feedback information generated during a previous measurement period. The feedback information is used to adjust a clock used to generate a local signal.