Direction of Arrival Estimation for Multi-Path Rejection in GPS
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Solution Overview
Problem
Satellite positioning systems face significant errors due to multi-path interference from signal reflections off walls, particularly in urban environments, leading to inaccurate position calculations and billing issues in geo-located road toll applications, where existing antenna array methods are inefficient due to size constraints and incorrect assumptions about reflection angles.
Innovation Solution
A method using a three-dimensional geographical map and an array of antennas to estimate the direction of arrival of navigation signals, involving ray casting to determine the number of reflections and initializing an algorithm to calculate reflection angles, which then adjusts the antenna pattern to attenuate multi-path signals, thereby improving position accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an array of antennas is used to estimate the direction of arrival of navigation signals, then the rejection of multi-paths is improved, but the device complexity increases
Solution Approach 1:
The antenna array is divided into multiple individual antennas (at least two) positioned at different locations on the moving object. Each antenna independently receives navigation signals, and the receiver processes the signals from multiple antennas to estimate direction of arrival. This segmentation allows the system to achieve multi-path rejection capability through spatial distribution of reception elements rather than requiring a single complex antenna structure.
Solution Approach 2:
The patent introduces the spatial dimension by positioning antennas at different locations and using direction of arrival estimation to determine the angular position of reflected signals. The receiver analyzes the phase differences and arrival times of signals across the spatially distributed antennas to calculate the direction from which reflected signals arrive, enabling multi-path rejection through spatial processing rather than temporal or amplitude processing alone.
2Reliability
If the number of antennas in the array is increased to improve directivity, then the rejection of multi-paths is improved, but the size of the array increases
Solution Approach 1:
The patent employs at least two antennas, which is a partial configuration that provides sufficient direction of arrival estimation capability without requiring a full array of many antennas. This partial action approach achieves the necessary multi-path rejection performance through careful signal processing and geometric analysis of the limited antenna positions, avoiding the need for large-scale physical arrays.
Solution Approach 2:
The system changes the operational parameters by utilizing the spatial arrangement of a small number of antennas and processing the phase and time difference information to achieve direction of arrival estimation. Instead of relying on the physical size of the antenna array, the system optimizes the parameter extraction from the limited antenna configurations through sophisticated signal processing algorithms.
3Productivity
If conventional antenna array methods are used, then the positioning can be performed, but the measurement precision is reduced due to incorrect assumptions about reflection angles
Solution Approach 1:
The receiver continuously monitors the navigation signals and the estimated direction of arrival, comparing the calculated position with expected geometric relationships. The system uses feedback from the signal processing to refine the direction of arrival estimates and adjust the positioning calculations, correcting for incorrect assumptions about reflection angles through iterative refinement and geometric validation.
Solution Approach 2:
The patent replaces mechanical or physical assumptions about reflection geometry with computational methods. Instead of relying on predefined mechanical models of signal reflection, the system uses signal processing techniques to calculate the actual direction of arrival from the observed phase and time differences, substituting physical geometric assumptions with data-driven computational analysis that adapts to actual reflection conditions.
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 method enhances the accuracy of position calculations by effectively rejecting multi-paths and reducing measurement errors, ensuring reliable road toll billing even in complex urban settings.
Implementation Method 1
The receiver, placed in a moving object, receives the navigation signals on an antenna of the array of antennas and estimates a position of the receiver
Implementation Method 2
estimating the direction of arrival of navigation signals at a receiver after reflection by walls
Data Source
AI summary
A method includes estimating a position of a receiver, aboard a moving object, on the basis of the navigation signals emitted by satellites received by an antenna in an antenna array placed on the moving object, and using a three-dimensional geographical map to deduce, geometrically, on the basis of the position of the receiver and of a ray casting starting from the receiver, the number of paths reflected on walls of buildings present in a scene corresponding to an environment surrounding the receiver. The determined number of reflected paths is used to initialize an algorithm for estimating angles of arrival of multi-paths to deduce therefrom angles of arrival of the paths reflected on the walls before reaching the receiver. Optionally, the method can comprise making it possible to bound the distance information error due to a multi-path to render the estimation of direction of arrival of the signals more efficacious.