Positioning Accuracy via Doppler-Range Consistency
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Solution Overview
Problem
Existing positioning systems using ultrasonic signals for mobile receivers face challenges in achieving high accuracy due to motion-induced phase shifts and spurious signals from reflections, which affect the precision of position determination.
Innovation Solution
The method involves transmitting transmitter-specific identification signals, processing their times of arrival to determine range data, calculating Doppler-shift information to obtain velocity data, integrating velocity data to estimate distances, and using range error data to weight contributions in an optimization problem for improved position estimation, effectively filtering spurious signals by prioritizing range estimates with high correlation between time-of-flight and Doppler-shift measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase-adjusted cross-correlation is used to decode received signals, then positioning accuracy is improved, but the system becomes vulnerable to spurious signals from reflections and multiple signal paths
Solution Approach 1:
The patent converts the harmful effect of Doppler shifts and signal reflections into a useful filtering mechanism. By integrating Doppler-shift information with range data, the system identifies and weights measurements based on their consistency, effectively using the presence of motion-induced effects to distinguish valid signals from spurious reflected signals. This transforms what was previously a source of error into a discriminative feature for signal validation.
Solution Approach 2:
The system implements feedback by using range error data derived from comparing independent range estimates (time-of-flight vs. Doppler-based) to weight subsequent measurements. Measurements showing high consistency between different estimation methods receive higher weights, while inconsistent measurements are downweighted. This feedback loop continuously refines the positioning accuracy by learning from measurement consistency patterns.
2Quantity of substance
If multiple signal paths including reflections are present, then signal reception is enhanced, but measurement precision deteriorates due to spurious signals
Solution Approach 1:
The patent applies local quality by assigning different weights to different measurements based on their individual consistency characteristics. Rather than treating all measurements uniformly, the system evaluates each range estimate's reliability through range error data and applies localized weighting. This allows strong reflected signals to be included in the positioning calculation only when their derived range estimates show high consistency, while rejecting strong but spurious signals that fail the consistency check.
3Measurement precision
If velocity data from Doppler shift is integrated to determine distance, then positioning accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges two independent measurement approaches (time-of-flight range estimation and Doppler-based velocity integration) into a unified positioning framework. By combining these methods and evaluating their mutual consistency through range error analysis, the system achieves enhanced accuracy without requiring a completely new complex system. The integration leverages existing signal processing capabilities in a synergistic manner.
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 enhances positioning accuracy by filtering out spurious signals and improving the consistency of distance measurements, leading to more precise location determination of mobile receiver units, especially in environments with reflections and multiple signal paths.
Implementation Method 1
determining a time of arrival of each of a plurality of the identification signals received by the mobile receiver unit from the transmitter unit during a time window; processing the times of arrival to determine range data representative of a plurality of distances between the transmitter unit and the mobile receiver unit
Implementation Method 2
determining Doppler-shift information from the plurality of received identification signals; using the Doppler-shift information to determine velocity data representative of one or more values of a component of velocity of the mobile receiver unit
Data Source
AI summary
In a positioning system, a plurality of transmitter units (2, 3, 4, 5) transmit respective transmitter-specific identification signals at intervals, which are received at a mobile receiver unit (7). A processing system (7; 9) identifies the transmitter unit that transmitted each received identification signal, and, for each signal, determines range data from time of arrival data and determines distance data from Doppler shift information. The range data and distance data are compared to determine range error data. A position estimate for the mobile receiver unit (7) is determined by solving an optimisation problem using range estimates determined for the plurality of transmitter units, weighted in dependence on the range error data.