Time of Arrival Difference Calculation for Wireless Location
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Solution Overview
Problem
Current wireless communication systems face challenges in accurately determining the location of mobile devices and transmitters due to clock skews and drifts, which affect time of arrival measurements, especially in environments with multiple access points and varying communication protocols.
Innovation Solution
A system and method that utilize a propagation time measurement scheme to overcome clock skews and drifts by processing signals from multiple transmitters, calculating differences in time of arrival independent of internal clocks, and employing hyperbolic navigation to determine locations based on time differences between signals received from pairs of transmitters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If time of arrival measurements are used for location determination in wireless communication systems, then location estimation can be achieved, but clock skews and drifts cause measurement inaccuracies
Solution Approach 1:
The patent uses a reference signal as an intermediary to establish a common time reference between transmitters and receivers. By having all devices synchronize their measurements to this shared reference, the system eliminates the need for perfectly synchronized clocks while maintaining measurement accuracy. The reference signal acts as a mediator that translates local clock times into a common reference frame.
Solution Approach 2:
The system changes the measurement parameter from absolute time of arrival (which is sensitive to clock skew) to time difference of arrival relative to a reference signal. This parameter transformation makes the measurement invariant to clock frequency offsets and drifts, as the differential measurement cancels out the common-mode clock errors.
2Ease of operation
If asynchronous communication between transmitters and receivers is allowed, then system flexibility and ease of operation improve, but clock synchronization becomes difficult
Solution Approach 1:
The system enables receivers to autonomously determine their location without requiring centralized time synchronization. Each receiver independently measures time differences relative to the reference signal and calculates its position using hyperbolic navigation. This self-service approach maintains asynchronous operation while achieving precise location determination.
Solution Approach 2:
The patent establishes a reference signal transmission as a preliminary action that sets up the time reference framework before actual location measurements are taken. This preliminary reference signal allows subsequent measurements to be made asynchronously while still being reference-frame consistent, enabling flexible operation without sacrificing measurement precision.
3Reliability
If multiple transmitters are used for location determination, then measurement redundancy and reliability improve, but the complexity of processing multiple time of arrival signals increases
Solution Approach 1:
The patent segments the location determination problem into independent pairwise comparisons between the unknown transmitter and each reference transmitter. By processing each reference transmitter separately and combining results through hyperbolic intersection, the system maintains reliability through multiple measurements while managing complexity through modular, incremental processing rather than attempting to process all signals simultaneously.
Data Source
AI summary
In at least one embodiment, a system for wireless communication is provided. The system includes a first transceiver and a first mobile device. The first mobile device includes the first transceiver and is programmed to receive a first wireless signal and a second wireless signal and to process the first wireless signal and the second wireless signal based on a first internal clock associated with the first mobile device. The first mobile device is further programmed to determine a time of arrival (TOA) of the first wireless signal to provide a first TOA signal and to determine the TOA of the second wireless signal to provide a second TOA signal. The first mobile device is further programmed to obtain a difference between the first TOA signal and the second TOA signal to provide a first difference TOA signal that is independent of the first internal clock.