Wireless Locationing Correction Factor for Signal Contour Accuracy
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Solution Overview
Problem
Existing methods for determining the physical location of wireless devices in WLANs, such as mathematical modeling and fingerprinting, face significant prediction errors due to incongruent signal coverage areas between access points and mobile devices, and variations in RF properties between test and actual devices.
Innovation Solution
The implementation of a correction factor in location determination algorithms that accounts for the differences in transmit power and antenna gain between access points and mobile units, applied in both mathematical modeling and fingerprinting approaches, to accurately calculate signal strength contours and improve location prediction accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mathematical modeling approach is used to determine location based on AP transmit power and antenna gain, then location prediction can be performed, but significant prediction error occurs due to non-congruent coverage areas between AP and mobile device
Solution Approach 1:
The patent modifies the mathematical modeling approach by introducing a correction factor that adjusts the relationship between AP and mobile device coverage areas. This correction factor accounts for the non-congruent nature of their respective signal coverage, transforming the original model parameters to compensate for the discrepancy and thereby reducing prediction errors in location determination.
2Measurement precision
If fingerprinting approach is used with test mobile device data, then location determination can be performed, but prediction error increases when actual mobile device has different RF properties than test device
Solution Approach 1:
The patent enhances the fingerprinting approach by incorporating a correction factor that adjusts for differences in RF properties between test and actual mobile devices. This correction factor modifies the fingerprint matching process to account for variations in transmit power, antenna gain, and other RF characteristics, enabling accurate location determination even when the actual device differs from the test device used to create the fingerprint database.
3Measurement precision
If correction factor is applied to account for transmit power and antenna gain differences, then location accuracy is improved, but calculation complexity increases
Solution Approach 1:
The patent introduces a correction factor that, while adding a computational step, does so in a manner that maintains algorithmic efficiency. The correction factor is derived from known device specifications (transmit power and antenna gain) and applied as a straightforward adjustment to the coverage area calculations, rather than requiring complex iterative optimization or additional measurement campaigns.
Data Source
AI summary
Methods and systems are provided for determining the location of a first wireless device (e.g., a mobile unit) within a wireless network comprising a second wireless device (e.g., an access point). The method includes determining a signal strength contour associated with RF communication between the access point and the mobile unit, and adding a correction factor to the signal strength contour to produce a corrected signal strength contour, wherein the correction factor includes the sums of the differences between the transmit power and the antenna gain associated with the mobile unit and the access point. In an alternate scheme involving stored fingerprint data, a correction factor is introduced based on the differences between antenna gains and transmit power associated with the mobile unit under consideration and the mobile unit used for generating the fingerprint data. The systems and methods disclosed herein are applicable, for example, to networks operating in accordance with 802.11, RFID, WiMax, WAN, Bluetooth, Zigbee, UWB, and the like.