GNSS Receiver Multipath Interference Correction
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Solution Overview
Problem
Global navigation satellite system (GNSS) receivers face inaccuracies in location determination due to multipath interference, where reflected signals interfere with direct signals, especially in urban environments with tall buildings, causing interference and distortion.
Innovation Solution
A processor determines the differences in signal path lengths and applies corrections to remove the effects of multipath interference by analyzing feasible signal paths and using a tree data structure to limit calculations, designating statistically stable satellites and reducing the complexity of signal propagation from three-dimensional to two-dimensional.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional GNSS receivers use direct line-of-sight signals for location determination, then positioning accuracy is improved, but the system cannot operate in urban environments with tall buildings blocking direct signals
Solution Approach 1:
The patent converts the harmful multipath effect into a beneficial tool by using reflected signals that would normally be considered interference. The system identifies and utilizes NLOS signal paths that bounce off buildings and other structures to determine location in urban canyons where direct LOS signals are blocked, thereby transforming an adverse environmental factor into a useful positioning mechanism
Solution Approach 2:
The patent transitions from traditional two-dimensional horizontal positioning to three-dimensional positioning by incorporating vertical path information from reflected signals. The system models signal propagation in 3D space, accounting for reflections off building facades at different angles and heights, enabling accurate location determination in environments where horizontal LOS is blocked but vertical reflection paths exist
2Adaptability or versatility
If GNSS receivers process multiple signal paths including reflected signals, then location determination is possible in urban areas, but multipath interference causes inaccuracies in timing calculations
Solution Approach 1:
The patent segments the signal processing into distinct LOS and NLOS path analyses. The system separately identifies direct path signals and reflected path signals, processes them through different computational models, and combines the results. This segmentation allows the receiver to handle multiple signal paths without allowing multipath interference to corrupt the timing measurements of individual paths
Solution Approach 2:
The patent introduces an intermediary modeling layer that represents the physical environment (buildings, reflectors) between the satellite and receiver. This intermediary model allows the system to predict expected NLOS path characteristics and compare them against actual received signals, thereby identifying and correcting for multipath effects in the timing calculations
3Measurement precision
If the receiver analyzes all possible signal paths to correct for multipath interference, then positioning accuracy in urban areas is improved, but computational complexity increases significantly
Solution Approach 1:
The patent performs preliminary action by pre-modeling the urban environment geometry and pre-calculating expected NLOS signal paths based on building layouts and satellite positions. This pre-computation allows the receiver to quickly identify relevant reflected paths during signal processing without having to analyze all possible paths in real-time, thereby reducing computational complexity while maintaining accuracy
Solution Approach 2:
The patent changes key parameters such as signal strength thresholds, path length tolerances, and reflection angle ranges to filter out improbable NLOS paths. By adjusting these parameters dynamically based on environmental context and signal quality metrics, the system reduces the number of paths requiring detailed analysis, thereby managing computational complexity while preserving positioning accuracy
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 enables accurate location determination in urban areas where direct line-of-sight signals are unavailable, improving positioning accuracy by correcting for signal reflections and reducing multipath interference.
Implementation Method 1
signals from a transmitter sometimes bounce off from physical objects before reaching an antenna of a receiver. Both a direct line-of-sight (LOS) signal and reflected signals may arrive at the antenna of the receiver at different times. This phenomenon is referred to as multipath interference.
Data Source
AI summary
Systems, methods, and computer program products for determining a location from non-line-of-sight (NLOS) signals are described. A processor can determine that multipath interferences of a signal reaching a receiver through different paths that are close in lengths may be mistakenly interpreted as additional time shift, (e.g., additional time delay or, in some cases, time advance) of the signal in calculating a timing of the signal. The processor can determine the possible differences between path lengths and then determine an amount of the additional time shift. The processor can determine a shift correction to remove effects caused by the additional time delay from the timing calculation.