Time-of-Flight Positioning via Bidirectional Channel Feedback
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Solution Overview
Problem
Existing Time-of-Flight (ToF) positioning methods for indoor navigation introduce errors due to only one side of the channel being considered in calculations, leading to location determination inaccuracies of tens of meters, as they do not account for the combined effects of both sides of the communication channel.
Innovation Solution
Implementing a method where an initiating station sends a frame to a responding station, which provides feedback information, allowing the initiator to determine channel information for both sides of the channel, thereby performing ToF calculations accurately and using this feedback for beamforming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If only one side of the channel is considered in ToF calculations, then the calculation process is simplified, but location determination accuracy deteriorates with errors of tens of meters
Solution Approach 1:
The patent implements a feedback mechanism where the responding station sends channel information back to the initiating station. This feedback allows the initiator to obtain channel characteristics from both directions (initiator-to-responder and responder-to-initiator), enabling accurate ToF calculations that account for bidirectional channel effects without requiring complex hardware changes
Solution Approach 2:
The patent uses channel information as an intermediary element to transfer knowledge about the communication medium between stations. By exchanging channel state information through feedback frames, the system enables both stations to understand the bidirectional channel characteristics, which serves as a mediator to achieve accurate positioning without direct complex measurements
2Measurement precision
If channel feedback is implemented for accurate ToF calculation, then location determination accuracy improves, but device complexity increases due to additional feedback mechanisms
Solution Approach 1:
The patent makes the feedback mechanism multi-functional by using the same channel feedback information for both ToF calculation and beamforming operations. The channel information exchanged between stations serves dual purposes: enabling accurate distance measurement and supporting spatial beamforming, thereby reducing the need for separate dedicated feedback channels or mechanisms
Solution Approach 2:
The patent changes the parameter being measured from unidirectional channel characteristics to bidirectional channel characteristics through feedback. By incorporating the responding station's channel information into the calculation, the system transforms the measurement parameter to include both directions of signal propagation, improving accuracy without requiring fundamentally new measurement techniques
Data Source
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AI summary
A method and system for time-of-flight (ToF) positioning in an IEEE 802.11 network comprises a responder station to transmit samples of preambles as the preambles are received. The samples represent channel information. The preambles comprise extension high-throughput long training fields (HT-LTFs). An initiator station is arranged to perform a time-of-arrival calculation based at least in part on an analysis of the channel information.