Wireless Localization Using Time Difference of Arrival and Ellipse Intersection
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Solution Overview
Problem
Current localization techniques for wireless devices face challenges in accurately determining the location of client devices in wireless networks without requiring complex synchronization and communication overhead, especially in scenarios where time-of-day synchronization is not feasible.
Innovation Solution
A system and method utilizing time difference of arrival (TDOA) between signals transmitted by a transmitter station and received by multiple receiver stations, which calculate ellipses with focal points at the transmitter and receiver stations to estimate the client device's location using intersection points, allowing for efficient location determination without communication overhead and with asynchronous clock operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If time-of-day synchronization is used for localization, then location accuracy is improved, but system complexity and communication overhead increase
Solution Approach 1:
The patent extracts the time synchronization requirement from the localization system by using TDOA measurements that are independent of absolute time references. Each receiver independently measures the time difference between the transmitter signal and its own signal, eliminating the need for centralized time-of-day synchronization while maintaining location accuracy.
Solution Approach 2:
The patent introduces TDOA measurements as an intermediary that bridges the gap between signal transmission and location determination without requiring direct time synchronization. The TDOA values serve as intermediate parameters that capture the necessary temporal information while being independent of absolute time references.
2Measurement precision
If complex synchronization protocols are implemented, then location accuracy is improved, but computation overhead increases
Solution Approach 1:
The patent enables each receiver to independently compute TDOA measurements and contribute to the location solution without requiring complex centralized processing. The receivers self-organize the localization process by independently measuring TDOA values and the location server simply combines these measurements using ellipse intersection geometry, minimizing computation overhead.
Solution Approach 2:
The patent replaces complex synchronization protocols with a geometric approach based on ellipse intersections. Instead of using sophisticated time synchronization mechanisms, the system uses the geometric properties of ellipses defined by TDOA measurements to determine location, substituting mechanical/time-based synchronization with geometric computation.
3Device complexity
If asynchronous clock operation is allowed, then system simplicity is improved, but location measurement precision deteriorates
Solution Approach 1:
The patent inverts the traditional approach by not trying to synchronize clocks to enable localization, but rather using the asynchronous clock differences themselves as the basis for TDOA measurements. The system accepts clock asynchrony and uses it to define the ellipses for location determination, turning a potential problem into the foundation of the solution.
Data Source
AI summary
This invention relates to methods and systems for localization. It is particularly concerned with localization techniques based on time difference of arrival for wireless devices. Embodiments of the invention relate to techniques in which a transmitter transmits periodic distinguishable signals which are relayed upon receipt by the client whose location is sought in a form distinguishable from that of the transmitter. Signals from both the transmitter and the client are received by at least three signal receivers which generate a time difference of arrival based on the difference taken for a signal to reach the receiver directly and via the client. Further embodiments of the invention provide a phase detector in the receivers to determine the time difference of arrival between the signals.