Wireless Locationing via Access Point Assisted Timing
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Solution Overview
Problem
Current wireless network technologies face challenges in accurately determining the location of network devices without requiring multiple frame exchanges and clock synchronization, especially with legacy devices that do not support fine timing measurement protocols, and are limited by insufficient time resolution for higher bandwidth signals.
Innovation Solution
The system employs an access point assisted by other network devices at known distances and locations, which snoops frame exchanges and provides feedback to determine the location of a client station using a single frame exchange, compensating for clock offsets and analog delays without performing clock synchronization, and can implement either Time Difference of Arrival (TDoA) or Time of Flight (ToF) methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple frame exchanges are used for location determination, then locationing accuracy can be improved, but network overhead increases and time consumption increases
Solution Approach 1:
The system segments the location determination process by having multiple access points independently measure timing information from frame exchanges with a client station. Each access point performs separate timing measurements (ToA, ToD) and calculations independently, then the client station combines these segmented measurements to determine its location. This segmentation allows accurate locationing without requiring multiple coordinated frame exchanges between the client and a single access point.
Solution Approach 2:
The timing measurement mechanism is designed to serve multiple functions simultaneously: it provides both location determination and clock offset compensation. The same frame exchanges used for measuring time of arrival and time of departure also enable calculation of clock offsets between access points and the client station. This multi-functionality reduces the need for separate synchronization protocols, thereby reducing network overhead while maintaining locationing accuracy.
2Measurement precision
If clock synchronization is performed between access points and client station, then timing measurement accuracy can be improved, but device complexity and protocol requirements increase
Solution Approach 1:
The system enables each access point and the client station to independently determine their own clock offsets through self-service measurements. Instead of requiring centralized clock synchronization, each device uses the timing information from normal frame exchanges to calculate its offset relative to others. The client station autonomously combines timing measurements from multiple access points to determine both its location and clock relationships, eliminating the need for complex synchronization protocols.
Solution Approach 2:
The system uses feedback from timing measurements to continuously compensate for clock offsets. Each access point measures the time of arrival and time of departure of frames, and these measurements feed back into calculations that determine clock offsets. This feedback mechanism allows the system to maintain timing measurement accuracy without requiring pre-synchronization, as the offset information is continuously derived from actual frame exchange timing data.
3Measurement precision
If fine timing measurement protocols are used, then locationing accuracy can be improved, but compatibility with legacy devices is lost
Solution Approach 1:
The timing measurement mechanism is designed to work with any device that can participate in standard frame exchanges, making it universal across legacy and modern devices. The system uses basic timing information (time of arrival and time of departure) that can be extracted from any frame exchange, without requiring specialized fine timing measurement protocol support. This universality allows accurate locationing of both legacy devices and modern devices with fine timing measurement capability.
Solution Approach 2:
The system adapts its measurement approach based on device capabilities by changing the parameters used in timing measurements. For legacy devices, it relies on standard frame exchange timing information. For modern devices with fine timing measurement support, it can utilize more precise timing parameters. This parameter adaptation allows the system to maintain high locationing accuracy while ensuring compatibility across different device generations and capabilities.
4Measurement precision
If time resolution is improved to 0.1 ns, then locationing accuracy can be improved, but measurement and processing complexity increases
Solution Approach 1:
The system replaces complex hardware-based high-resolution timing mechanisms with software-based timing measurement and processing. Instead of requiring specialized hardware capable of 0.1 ns resolution, the system achieves this precision through careful software measurement of frame exchange timing and mathematical processing of the collected data. This substitution reduces hardware complexity while maintaining the required time resolution for accurate locationing.
Solution Approach 2:
The system performs preliminary measurements of timing information during normal frame exchanges before the actual location calculation. By collecting and storing time of arrival and time of departure data during routine operations, the system prepares the necessary high-precision timing information in advance. This preliminary action allows the system to achieve 0.1 ns time resolution without requiring complex real-time processing, as the measurements are already captured and ready for location calculation.
Data Source
AI summary
A first access point including a receiver, a transmitter, a feedback module, and a location determining module. The receiver receives a first frame from a client station. The transmitter transmits a second frame to the client station. The first and second frames are also received by second and third devices, which are located at predetermined locations. The feedback module receives a first feedback from the client station including times of departure and arrival of the first and second frames at the client station, and a second feedback from the second and third devices including times of arrival of the first and second frames at the second device and the third device. The location determining module determines a location of the client station based on the times of arrival and departure of the first and second frames at the first access point, the first and second feedbacks, and the predetermined locations.