Wireless Clock Synchronization for Accurate Client Location
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Solution Overview
Problem
Current wireless networks, such as those adhering to IEEE 802.11 and 802.3 standards, face challenges in accurately locating clients due to lack of precise clock synchronization and variations in radio output power, leading to inaccurate positioning using existing methods like time difference of arrival and received signal strength indicator techniques.
Innovation Solution
A system and method that synchronizes clocks across access points using a precision clock and time domain reflectometry, distributing a common precise time reference and employing a time difference of arrival technique with oversampling to accurately determine client location, incorporating a high-frequency clock and periodic timing synchronization pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If network time protocols or simple network time protocols are used for time synchronization, then ease of operation is improved, but measurement precision deteriorates due to 1 microsecond variation translating to approximately 983 feet location error
Solution Approach 1:
The patent changes the time synchronization parameter from standard network time protocols (1 microsecond precision) to a high-frequency clock system operating at 10 MHz or higher, achieving nanosecond-level precision. This parameter change in clock frequency directly resolves the contradiction by providing both automated operation and sufficient measurement precision for accurate client location within 30 feet.
Solution Approach 2:
The patent introduces a dedicated time synchronization intermediary system consisting of a clock source, time distribution network, and synchronization protocol that mediates between the high-frequency clock and access points. This intermediary ensures precise time reference distribution across all network entities while maintaining ease of operation through automated synchronization processes.
2Ease of operation
If received signal strength indicator information is used for location determination, then ease of operation is improved, but measurement precision deteriorates due to radio output power variations causing different received signal strength indicator voltages for radios in the same location
Solution Approach 1:
The patent introduces time difference of arrival measurement as an intermediary method that bypasses the unreliable received signal strength indicator approach. By using precisely synchronized clocks at access points and measuring arrival time differences of client transmissions, the system achieves accurate location determination independent of radio output power variations.
Solution Approach 2:
The patent substitutes the signal strength-based mechanical measurement system with a time-based electromagnetic measurement system. Instead of measuring voltage levels that vary with power output, the system measures time intervals with nanosecond precision, replacing an unreliable physical measurement with a more precise temporal measurement.
3Device complexity
If standard clock synchronization is used in wireless networks, then device complexity is reduced, but measurement precision deteriorates due to insufficient clock correlation in switches and access points
Solution Approach 1:
The patent segments the clock synchronization system into distinct functional components: a dedicated clock source, a time distribution network, and synchronized access points. This segmentation allows each component to be optimized independently - the clock source provides high-frequency precision, the distribution network handles time reference propagation, and access points perform local time stamping, achieving high precision without excessive overall complexity.
Data Source
AI summary
A system for locating a client in a wireless network. The system includes at least three access points. Each access point is adapted to wirelessly communicate with a client having a location using packeted data, be placed in wired data communication within a selected data network; and to share a common precise time reference using the selected data network. The system further includes a switch adapted to translate the relative position of the access points based on a shared common precise time reference and to calculate the location of the client based on a transmission from the client.