Radiolocation via Calibrated Path Loss Models
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Solution Overview
Problem
Existing methods for radiolocation in wireless networks, such as GPS, TDOA estimation, and RF modeling, require additional hardware, precise synchronization, or detailed building layouts, making them costly and inefficient for indoor use and rogue access point detection.
Innovation Solution
A method using path loss measurements between known and unknown wireless stations to determine the location of client stations or potential rogue access points, utilizing existing signal strength measurements and calibrating an ideal path loss model with minimal training, allowing automatic calibration by access points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS is used for radiolocation, then location accuracy is improved, but additional GPS hardware is required and indoor reception is poor
Solution Approach 1:
The patent makes existing WLAN radio hardware perform multiple functions: it serves both for wireless communication and for radiolocation measurements. By using the same antenna and receiver for both data transmission and location determination, the system eliminates the need for separate GPS hardware while maintaining location accuracy through path loss calculations based on signal strength measurements.
2Measurement precision
If TDOA estimation is used for radiolocation, then location accuracy is improved, but precise time synchronization is required which needs non-standard hardware
Solution Approach 1:
The patent replaces the time-synchronization-based TDOA method with a signal strength-based path loss method. Instead of measuring time differences of arrival which require precise clock synchronization, the system measures received signal strength indicators (RSSI) and uses path loss models to determine location, thereby eliminating the need for specialized synchronization hardware.
3Measurement precision
If RF modeling is used for radiolocation, then location accuracy is improved, but detailed building layout and construction materials are required
Solution Approach 1:
The system performs self-calibration by having access points measure signal strengths between themselves and exchange location information. Through this mutual measurement process, the system automatically determines path loss characteristics specific to the environment without requiring external input about building layouts, wall locations, or construction materials.
Solution Approach 2:
The system performs preliminary path loss calibration during network deployment where access points measure signals to and from other known access points. This pre-established path loss model is then used for subsequent location determinations, eliminating the need for detailed environmental surveys before operation.
4Device complexity
If signal strength measurements are used for radiolocation, then device complexity is reduced, but time-consuming training measurements are required
Solution Approach 1:
The calibration measurements performed between access points serve dual purposes: they establish the path loss model for location determination and simultaneously provide data for managed deployment features. By reusing the same measurement infrastructure for multiple functions, the system reduces overall training time without requiring separate calibration procedures.
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
Enables accurate and cost-effective radiolocation with minimal additional hardware, reducing training time and requiring only standard radio hardware, effectively locating client stations and rogue access points within wireless networks.
Implementation Method 1
The method includes accepting an ideal path loss model and calibrating the ideal path loss model using path loss measurements between a first set and a second set of wireless stations
Data Source
AI summary
Determining the location of a station or potential rogue access point in a wireless network including accepting an ideal path loss model and calibrating the ideal model using path loss measurements between access points at known locations. The calibrating determines a calibrated path loss model between the access points. The method further includes determining path losses between the wireless station of unknown location and at least some of the access points. In the case the wireless station is a client station, the determining includes receiving measurements from the wireless station of unknown location measuring the received signal strengths as a result of respective transmissions from at least some of the access points at known respective transmit powers. In the case the wireless station is an potential rogue access point, the determining includes receiving measurements from at least some of the access points measuring the received signal strength at each of the access points resulting from transmission by the potential rogue access point for each of a set of assumed transmit powers for the potential rogue. The method further includes determining the likely location or locations of the wireless station using the measured path loss and the calibrated path loss model.