Geo-locating Moving Wireless Devices Using RTT and SSR
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Solution Overview
Problem
Existing geo-location methods for wireless devices, particularly those using IEEE 802.11 standards, face challenges in accurately determining the location of moving targets due to signal noise, weak signal strengths, and the need to account for movement, which can lead to errors in positioning.
Innovation Solution
A method and system that utilize round-trip times (RTTs) to determine the best-fit geo-location of a moving wireless device by assigning current target station parameters, including location and movement parameters, and calculating square residuals to minimize the sum of squared residuals (SSR), with non-linear fitting techniques such as the Levenberg-Marquardt process to adjust for movement, and performing an F-test to validate the accuracy of the geo-location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional RTT-based geo-location methods are used for moving wireless devices, then the location can be determined using basic time measurements, but the accuracy deteriorates due to signal noise, weak signals, and failure to account for movement
Solution Approach 1:
The patent applies dynamics by transitioning from static geo-location assumptions to dynamic modeling that accounts for device movement. The system estimates velocity vectors and applies motion compensation to RTT measurements, allowing accurate tracking of moving devices rather than assuming stationary positions. This resolves the contradiction by making the system adaptive to movement while maintaining measurement precision.
Solution Approach 2:
The patent changes parameters by introducing velocity vectors and motion state variables alongside traditional RTT measurements. By estimating and incorporating device velocity into the geo-location calculation, the system transforms static positioning parameters into dynamic ones, improving both accuracy and reliability for moving devices.
2Measurement precision
If multiple RTT measurements are taken to improve geo-location accuracy, then the precision improves, but the complexity of processing and analyzing the data increases
Solution Approach 1:
The patent simplifies processing by changing the parameter set to include velocity vectors and motion states. This transformation allows the system to process multiple RTT measurements more efficiently by incorporating motion compensation directly into the calculation model, reducing the computational burden compared to processing raw measurements without a unified motion-aware framework.
Solution Approach 2:
The system uses feedback by iteratively refining velocity estimates and position calculations based on successive RTT measurements. This feedback loop allows the system to converge on accurate geo-location while systematically processing multiple measurements, managing complexity through structured iteration rather than brute-force computation.
3Measurement precision
If movement parameters are incorporated into the geo-location calculation, then the accuracy for moving devices improves, but the computational requirements and processing time increase
Solution Approach 1:
The patent applies preliminary action by pre-estimating velocity vectors from initial RTT measurements before performing detailed geo-location calculations. This preliminary velocity estimation is then used to compensate for device movement in subsequent position calculations, reducing the computational burden and time required for full motion-compensated geo-location while maintaining 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 provides accurate geo-location of moving wireless devices by accounting for movement parameters, reducing errors associated with signal noise and weak signals, and improving the precision of geo-location determination.
Implementation Method 1
measuring a plurality of round-trip times, RTTs, each RTT being a time elapsed between a transmission of a ranging packet and a reception of a response packet
Data Source
AI summary
A method in a wireless device (WD) for determining a best-fit geo-location of a target station is described. The best-fit geo-location is determined using a plurality of round-trip times (RTTs). The target station is movable. The method includes assigning values to current target station parameters. The current target station parameters include a current location for the target station and movement parameters. A plurality of square residuals is determined based at least in part on the current target station parameters. Each square residual of the plurality of square residuals corresponds to one RTT. A minimum of a sum of squared residuals (SSR) is determined based at least on the plurality of square residuals. best-fit parameters are determined based at least in part on the determined minimum of the SSR. In addition, the best-fit geo-location of the target station is determined based at least on the best-fit parameters.