GNSS Multipath Mitigation via Signal Segmentation
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Solution Overview
Problem
Global Navigation Satellite System (GNSS) receivers face position-solution errors due to multipath signals, particularly in urban environments, where Non-Line of Sight (NLOS) signals interfere with Line of Sight (LOS) signals, affecting code-tracking and range-rate measurements.
Innovation Solution
A GNSS receiver with a wideband signal correlation module and a multipath-mitigation module that identifies and separates LOS and NLOS signal components using High-Resolution Power (HRP), High-Resolution Code (HRC), and High-Resolution Carrier (HRCC) functions, allowing for accurate estimation of code phase and carrier phase, and subsequent generation of improved range and range-rate measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If NLOS signal components are tracked along with LOS signals, then the receiver can maintain signal tracking in challenging environments, but position-solution error and range error increase due to multipath interference
Solution Approach 1:
The patent segments the received GNSS signal into multiple components by identifying distinct signal paths. The correlation module separates LOS and NLOS signals based on their different time delays and path characteristics, allowing independent processing of each component to eliminate multipath interference from position calculations
Solution Approach 2:
The patent extracts only the LOS signal component from the mixed received signal for position calculation. By identifying and isolating the direct path signal characteristics (such as earliest arrival time and strongest correlation peak), the system excludes NLOS components from the navigation solution, thereby improving accuracy while maintaining tracking of all signals
2Measurement precision
If wideband correlation is used to resolve multipath signals, then LOS and NLOS components can be separated, but the device complexity and computational load increase
Solution Approach 1:
The patent performs preliminary wideband correlation processing to identify and characterize multipath components before the main navigation calculation. By pre-separating LOS and NLOS signals and estimating their parameters (delay, amplitude, phase) in advance, the system reduces the computational burden during real-time position solving while maintaining high resolution capability
Solution Approach 2:
The patent extends the correlation processing into the time-delay dimension by using wideband correlation over an extended delay range. This additional dimensional processing allows separation of signals that would be indistinguishable in narrowband processing, resolving multipath without requiring complex spatial or frequency-domain techniques
3Reliability
If NLOS signal delay is used in code-tracking, then the receiver can maintain tracking loop stability, but range error increases directly proportionally to the NLOS delay
Solution Approach 1:
The patent extracts only the LOS signal component for code-tracking and range measurement by identifying the earliest arriving signal component with the strongest correlation peak. The tracking loops (code-tracking and carrier-tracking) are configured to lock onto this extracted LOS component exclusively, eliminating NLOS delay from the range calculation while maintaining loop stability through continuous tracking of the dominant signal path
Data Source
AI summary
A Global Navigation Satellite System (GNSS) receiver includes a wideband signal correlator and a multipath mitigator. The wideband signal correlator generates wideband correlation signals of at least one of a plurality of GNSS signals with respect to corresponding locally generated code replica signals in which a bandwidth of the wideband signal correlation module is at least about 20 MHz. The multipath mitigator determines a Line of Sight (LOS) signal from the wideband correlation signals. The GNNS receiver may include a narrowband signal correlator to generate narrowband correlation signals of the at least one GNSS signal with respect to corresponding locally generated code replica signals in which a bandwidth of the narrowband signal correlation module is less than about 6 MHz. The multipath mitigator further corrects a range and range-rate measurement generated from the narrowband correlation signals based on a code phase and a carrier estimated based on the LOS signal.