WiFi Ranging Clock Offset Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing wireless communication systems face inaccuracies in measuring propagation times between devices due to differences in clock frequencies, which affect the accuracy of ranging measurements.
Innovation Solution
Implementing a method where communication devices compensate for clock frequency offsets during ranging measurement sessions using a single clock reference, ensuring accurate timestamp calculations and propagation time determinations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If each communication device uses its own local clock frequency for timestamping, then device operation is simple and independent, but ranging measurement accuracy deteriorates due to clock frequency offsets between devices
Solution Approach 1:
The patent introduces a compensation mechanism that acts as an intermediary between the local clocks of different devices. The requester device calculates clock frequency offsets based on timestamps exchanged with the responder device, then uses these offsets to compensate timestamps before calculating propagation time. This intermediary compensation process eliminates the direct conflict between using independent local clocks and achieving accurate ranging measurements.
Solution Approach 2:
The patent changes the timestamp parameter by applying frequency offset compensation. Instead of using raw timestamps directly from local clocks, the system transforms these timestamps by compensating for clock frequency differences. This parameter transformation allows the system to maintain the simplicity of using local clocks while achieving the accuracy equivalent to using a synchronized reference clock.
2Measurement precision
If a single clock reference is used for all devices, then ranging measurement accuracy improves, but device complexity increases due to synchronization requirements
Solution Approach 1:
The patent implements self-service by allowing each device to independently calculate and compensate for its own clock frequency offset. The requester device performs the compensation calculations using timestamps it receives from the responder device, without requiring external synchronization infrastructure. This self-service approach achieves the accuracy benefits of a single clock reference while avoiding the complexity of centralized synchronization.
Solution Approach 2:
Instead of synchronizing clocks to a common reference (the conventional approach), the patent inverts the problem by allowing devices to run on independent clocks and then compensating for the differences. This inversion transforms the synchronization problem into a compensation problem, achieving the same accuracy goal with reduced complexity.
3Measurement precision
If clock frequency offset compensation is performed, then propagation time measurement accuracy improves, but processing complexity increases
Solution Approach 1:
The patent performs preliminary action by calculating the clock frequency offset before the final propagation time calculation. The system exchanges timestamps and computes the offset in advance, then applies this offset to compensate timestamps. This preliminary compensation simplifies the final propagation time calculation by eliminating the need for complex real-time synchronization processing.
Solution Approach 2:
The patent uses feedback by having the responder device send back timestamps that enable the requester device to calculate the clock frequency offset. This feedback loop provides the necessary information for compensation, allowing the system to achieve high accuracy through a relatively simple processing mechanism that leverages the existing communication exchange.
Data Source
AI summary
Timestamps associated with when transmissions are sent and received between a pair of communication devices are used to determine a distance between the pair of communication devices. The communication devices operate according to a wireless communication protocol, which specifies that a requester of a ranging measurement session is to compensate for a clock frequency offset between the pair of communication device and that a responder is not to compensate for the clock frequency offset. As part of the ranging measurement session, the responder sends feedback to the requester, where the feedback includes timestamps recorded by the responder. The timestamps in the feedback are not compensated for the clock frequency offset by the responder. After receiving the feedback, the requester compensates the timestamps in the feedback for the clock frequency offset before using the timestamps to calculate the distance between the pair of communication devices.