Scaled TDOA 3D Positioning for Rural Cells
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Solution Overview
Problem
Current TDOA positioning methods fail to provide three-dimensional accuracy meeting E-911 requirements in large rural cells with coarsely distributed sites, especially in hilly terrain, and lack support for scaling and translation of lateral variables, leading to accuracy issues and reliance on Assisted Global Navigation Satellite System (A-GNSS) which can be turned off by criminals.
Innovation Solution
A hybrid TDOA positioning method using a translated and scaled vertical surface model, based on polygon corners augmented with vertical information, and virtual points on 3D line segments, to improve accuracy and enable 3D positioning without relying on A-GNSS.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional TDOA positioning methods are used in large rural cells with coarsely distributed sites, then the positioning system can cover large areas, but the vertical positioning accuracy deteriorates and fails to meet E-911 requirements
Solution Approach 1:
The patent applies parameter changes by translating and scaling the lateral variables (x, y coordinates) in the vertical surface model. This transformation modifies the numerical properties of the model parameters, converting large rural cell coordinates into a normalized range that improves the conditioning of the least squares problem, thereby achieving both large area coverage and high vertical positioning accuracy
Solution Approach 2:
The patent incorporates virtual points on 3D line segments between polygon corners as additional boundary constraints. This adds dimensional information to the model by utilizing the third dimension (vertical/altitude) more effectively and adding intermediate points that regularize the surface fitting problem, improving vertical accuracy without compromising horizontal coverage
2Device complexity
If TDOA positioning is used without scaling and translation of lateral variables, then the model is simpler, but numerical properties deteriorate leading to accuracy issues
Solution Approach 1:
The patent introduces scaling and translation of lateral variables as a preprocessing step that transforms the coordinate system. This parameter transformation improves the numerical conditioning of the surface model without fundamentally changing the model structure, achieving better accuracy while maintaining relatively simple implementation
3Device complexity
If vertical surface model is used without additional boundary points, then the model is less complex, but regularization is insufficient leading to larger vertical errors
Solution Approach 1:
The patent segments the boundary of the cell polygon by introducing virtual points on the 3D line segments between the corners. This segmentation divides the continuous boundary into smaller segments with intermediate constraint points, providing better regularization for the vertical surface model fitting and reducing vertical positioning errors
Solution Approach 2:
The patent performs preliminary action by pre-defining the vertical surface model with incorporated boundary information before actual positioning calculations. The model is prepared with scaling, translation, and boundary point integration in advance, which regularizes the problem and improves accuracy during the positioning operation
Data Source
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AI summary
Systems and methods are disclosed herein that relate to positioning in a cellular communications system. In some embodiments, a method for determining a three dimensional location of a wireless device in a cellular communications network comprises obtaining a plurality of measurements for a wireless device, where the plurality of measurements are Time Difference of Arrival (TDOA) related measurements. The method further comprises computing a three dimensional position of the wireless device using the plurality of measurements and a vertical surface model, wherein the vertical surface model is a translated and scaled version of an initial vertical surface model. The new vertical surface model provides translation and scaling of the initial vertical surface model to a suitable range before it is used to determine the three dimensional position of the wireless device such that accuracy is improved, e.g., in large rural cells (1500, 1502, 1504).