WLAN Passive Geo-Location Clock Drift Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing geo-location methods for wireless local area network (WLAN) devices, particularly those based on IEEE 802.11 technology, face challenges in accurately determining the location of wireless devices due to clock drift and offset between the device and measuring stations, which affects the precision of Time of Arrival (TOA) measurements.
Innovation Solution
The method employs an assisted passive location scheme using a single measuring station that combines active and passive location techniques by determining the relative clock drift between the wireless device and the measuring station through the analysis of beacon transmissions, allowing for accurate location determination based on the calculated relative drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If passive location scheme is used to determine device location, then device can be located without transmitting packets, but clock drift between device and measuring station causes measurement precision degradation
Solution Approach 1:
The system performs preliminary actions by having the measuring station transmit ranging packets to the device before actual location measurement. This establishes a reference timing relationship and allows the device to synchronize its clock with the measuring station, thereby compensating for clock drift before passive location measurement begins. The ranging packet exchange occurs in advance to prepare the timing synchronization.
Solution Approach 2:
The device uses the ranging packet from the measuring station as feedback to adjust its clock timing. By receiving the known-time ranging packet and comparing it with its own clock, the device can calculate the time offset and drift, then compensate for these errors in subsequent beacon transmissions used for passive location measurement.
2Measurement precision
If multiple measuring devices are used to determine location through simultaneous TOA measurements, then location accuracy can be improved through TDOA calculation, but system complexity and cost increase
Solution Approach 1:
The system segments the location measurement function into two parts: a single measuring station performs active ranging to establish timing reference, while the device itself performs passive measurement of its own beacon transmissions at multiple locations. This divides the complex multi-station synchronization problem into simpler independent measurements.
Solution Approach 2:
The device serves itself by transmitting beacons that are passively measured during its normal operation. Instead of requiring multiple external measuring stations to actively probe the device, the device's own beacon transmissions are utilized for location determination, reducing the need for additional measuring infrastructure.
Data Source
AI summary
An assisted passive geo-location method and system for determining the location of a wireless device. The method includes passive location techniques in order to assist in determining the location of the wireless device and active techniques in order to assist in the calculation of the relative drift between the clock associated with the wireless device and the clock associated with the measuring station.