Reference Point Validation for Indoor Wireless Location Accuracy
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Solution Overview
Problem
Existing location systems relying on wireless access points (APs) face inaccuracies due to potential unintentional movement of APs, which are not reliably tracked, leading to errors in location estimates, particularly in indoor environments.
Innovation Solution
A method and system for validating the location of reference points by estimating distances between APs using measurement residuals and comparing them to known distances, employing techniques such as averaging and entropy estimation to detect any changes in AP positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reference points are used for location estimation, then location-based services can be provided, but the accuracy deteriorates when reference points are unintentionally moved
Solution Approach 1:
The system performs preliminary validation of reference point positions by exchanging wireless messages and calculating measurement residuals before using them for location estimation. This preliminary check detects any unintended movements of reference points, ensuring that only validated positions are used in subsequent location calculations, thereby maintaining accuracy despite potential physical displacements.
2Adaptability or versatility
If GPS is used for location services, then outdoor location can be determined, but it fails indoors due to signal blocking
Solution Approach 1:
The patent implements a universal location system that functions across both outdoor and indoor environments by using WiFi access points as reference points. The system validates these reference points through wireless message exchange and measurement residual analysis, enabling consistent location estimation whether the target is outdoors (complementing GPS) or indoors where GPS signals are blocked, thus achieving environmental versatility without sacrificing reliability.
3Device complexity
If reference point positions are assumed fixed, then location computation is simplified, but errors accumulate when positions change
Solution Approach 1:
The system implements feedback by continuously validating reference point positions through wireless message exchange and comparing measured distances against recorded positions. When measurement residuals indicate position changes, the system detects and corrects for these changes, providing feedback that maintains location estimation accuracy without requiring complete re-computation, thus balancing complexity and precision.
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
Ensures accurate location estimation by excluding APs that have moved from their known positions, thereby reducing errors in location-based services and enhancing the reliability of systems like E911.
Implementation Method 1
sending a wireless message between a second reference point and the first reference point and recording the times of sending and receipt of the wireless message; estimating, from the recorded times, an estimated distance between the first reference point and the second reference point
Data Source
AI summary
This invention relates to methods and systems for determining whether a reference point in a location system has changed used measurement residuals determined from an exchange of messages between reference points. In one embodiment a method of determining whether the location of a first one of a plurality of reference points used in a location system has changed is provided. The reference points each have a known initial position and the method includes the steps of: sending a wireless message between a second reference point and the first reference point and recording the times of sending and receipt of the wireless message; estimating, from the recorded times, an estimated distance between the first reference point and the second reference point; comparing the estimated distance to the actual distance between the known initial positions of the first and second reference points to determine a measurement residual; and determining, using the measurement residual, whether the location of the first reference point has changed.