Asymmetric Time Difference of Arrival Positioning Method
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Solution Overview
Problem
Existing positioning technologies, such as GPS and Wi-Fi fingerprinting, lack sub-metre accuracy and are not scalable for large numbers of devices due to high communication overhead and clock stability issues in indoor environments.
Innovation Solution
The Asymmetric Time Difference of Arrival (ATDOA) method, which uses two base stations of known location to calculate the time difference of arrival of signals between them and a device, allowing the device to determine its position without transmitting signals, thus reducing communication overhead and being resilient to clock errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS or Wi-Fi fingerprinting is used for positioning, then the system is simple to implement, but sub-metre accuracy cannot be achieved and indoor positioning is unavailable
Solution Approach 1:
The patent introduces base stations as intermediary elements between satellites/GPS and mobile devices. These base stations receive signals from GPS satellites and re-transmit them to mobile devices, enabling positioning functionality indoors where direct GPS signals are blocked. The base stations act as mediators that bridge the gap between outdoor GPS infrastructure and indoor positioning requirements.
Solution Approach 2:
The patent replaces the direct satellite-to-device signal path with an alternative signal transmission mechanism through base stations. Instead of relying on line-of-sight GPS signals, the system uses base stations to relay positioning signals, substituting the direct mechanical/electromagnetic path with an indirect transmission route that works in indoor environments.
2Measurement precision
If Ultra Wide Band with ATWR is used to achieve sub-metre accuracy, then positioning precision improves, but communication overhead increases and scalability is limited
Solution Approach 1:
The patent extracts the signal transmission function from mobile devices and concentrates it in base stations. Only base stations transmit signals, while mobile devices passively receive and process them. This extraction eliminates the need for bidirectional communication between devices and base stations, significantly reducing communication overhead while maintaining positioning accuracy.
Solution Approach 2:
The patent inverts the traditional ATWR approach where both device and base station transmit signals. Instead, only the base station transmits signals to multiple devices simultaneously, reversing the communication direction and reducing the total number of signal exchanges required in the system.
3Productivity
If multiple devices use ATWR simultaneously, then more devices can be positioned, but clock stability issues arise and accuracy degrades
Solution Approach 1:
The patent makes the base station a universal timing reference for all mobile devices in the system. The base station's clock serves multiple functions: signal transmission timing, synchronization reference for all devices, and positioning calculation baseline. This multi-functionality eliminates the need for each device to maintain independent clock synchronization, allowing multiple devices to be positioned simultaneously without clock stability issues.
4Productivity
If base stations transmit signals to multiple devices, then scalability improves, but signal coordination becomes complex
Solution Approach 1:
The patent implements a self-service mechanism where the base station automatically manages signal transmission to multiple devices without requiring complex coordination protocols. The base station transmits signals in a manner that all devices can independently receive and process, eliminating the need for handshaking, acknowledgment, or conflict resolution mechanisms between devices.
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
ATDOA achieves sub-millimetre accuracy and scalability by allowing multiple devices to determine their positions without increased communication or infrastructure, even in environments where GPS is unavailable, and is robust to clock errors and antenna delays.
Implementation Method 1
The communications system comprises a first base station and a second base station. The first base station is arranged to transmit a first signal to the second base station and the second base station is arranged receive the first signal and transmit a second signal to the first base station in response to the first signal.
Implementation Method 2
A delay time measuring unit is arranged to measure a first delay time as a time between receiving the first signal from the first base station and receiving the second signal from the second base station.
Data Source
AI summary
An exemplary communications system includes a first base station and a second base station. The first base station transmits a first signal to the second base station, and the second base station receives the first signal and transmits a second signal in response. The first base station receives the second signal and transmits a third signal in response. A receiving unit of a device receives the first, second, and third signals. The device measures a first delay time between receipt of the first signal and receipt of the second signal, and measures a first round trip time based on receipt of the second signal and the third signal. A second round trip time and a second delay time are determined and a first time difference of arrival is calculated based on the first round trip time, first delay time, second round trip time and second delay time.