RTT Calculation with Clock Drift Compensation
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Solution Overview
Problem
Clock drift in wireless devices configured according to IEEE 802.11 standards leads to imprecise and error-prone round trip time (RTT) calculations, affecting the precision of positioning and location-based applications.
Innovation Solution
Implementing systems and methods to calculate RTT between two wireless devices while accounting for their respective clock drifts, by broadcasting and averaging clock drift information to reduce the impact of clock errors, and using fine timing measurement frames with enhanced resolution and minimal overhead, allowing for precise RTT determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional RTT determination method is used with local clocks at each STA, then each device can operate independently with its own clock, but the RTT calculation becomes highly error-prone due to compounded clock drift errors
Solution Approach 1:
The patent implements a feedback mechanism where the receiving STA measures the actual arrival time of frames and calculates the clock drift error. This measured drift information is then fed back to the transmitting STA to compensate for future timing calculations, thereby improving RTT precision while maintaining independent clock operation
Solution Approach 2:
The patent introduces timing measurement frames as an intermediary carrier that transports clock drift information between STAs. These specialized frames enable the exchange of timing data without requiring direct clock synchronization, allowing error compensation while preserving operational independence
2Measurement precision
If clock synchronization is attempted between multiple STAs to reduce drift error, then RTT precision can be improved, but system complexity increases due to synchronization overhead
Solution Approach 1:
The patent extracts the clock drift measurement function from the RTT calculation process itself. By separating drift measurement into distinct timing measurement frames, the system achieves precision improvement without requiring complex continuous synchronization mechanisms between all STAs
Solution Approach 2:
The patent changes the approach from attempting to synchronize clock parameters to instead measuring and compensating for drift parameters. This parameter transformation allows precision improvement through drift correction rather than through complex synchronization protocols
Data Source
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AI summary
Systems and methods for calculating round trip time (RTT) between two wireless devices with respective clock drifts, while lowering the impact of the clock drifts on the RTT. A first RTT in a first direction is determined between a first wireless device and a second wireless device based on a first set of one or more messages exchanged between the first wireless device and the second wireless device. A second RTT in a second direction is determined between the second wireless device and the first wireless device based on a second set of one or more messages exchanged between the second wireless device and the first wireless device, and an average RTT of the first RTT and the second RTT is computed, wherein the average RTT has a low impact of the clock drifts.