Round Trip Time Measurement via Segmented Wi-Fi Frames
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Solution Overview
Problem
Current satellite positioning systems face challenges in accurately determining the position of mobile devices in indoor environments due to limited satellite signal availability and inefficiencies in measuring round trip time (RTT) for range calculations.
Innovation Solution
The implementation of specific message flows and frame structures between wireless stations (STAs) enables accurate RTT measurements using fewer messages, allowing for position determination through RTT calculations between STAs, including mobile devices and local transceivers, even in indoor environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional RTT measurement methods are used in indoor environments, then position determination can be performed, but measurement accuracy deteriorates due to signal reflections and multipath effects
Solution Approach 1:
The patent segments the RTT measurement process into multiple discrete message exchanges (four distinct frames: RTT Request, RTT Ack, RTT Response, RTT Ack) with specific timestamp markers (t1, t2, t3, t4) at each stage. This segmentation allows for precise calculation of RTT by measuring time intervals between specific events, improving measurement accuracy despite indoor signal challenges
Solution Approach 2:
The patent implements a feedback mechanism where each device echoes back its received timestamp to the other device. The first device sends t1 in the RTT Request frame, the second device receives it and sends t2 back in the RTT Ack frame, then the first device sends t3 and the second device sends t4 back. This feedback loop allows both devices to calculate RTT using the formula RTT = (t4 - t1) - (t3 - t2), compensating for processing delays and improving measurement accuracy
2Measurement precision
If more messages are used for RTT measurement, then measurement accuracy improves, but communication overhead and time consumption increase
Solution Approach 1:
The patent merges the RTT measurement function with existing Wi-Fi communication protocols (802.11). The RTT measurement is performed using standard Wi-Fi data frames (RTT Request, RTT Ack, RTT Response) that can be transmitted over existing wireless infrastructure. This merging allows RTT measurement to be performed without requiring separate dedicated measurement channels or additional infrastructure, reducing overall system complexity and deployment time
3Reliability
If satellite positioning systems are used for indoor positioning, then position determination is possible, but reliability deteriorates due to limited satellite signal availability
Solution Approach 1:
The patent uses local transceivers positioned at known locations within the indoor environment as intermediary reference points. Instead of relying on distant satellite signals that penetrate poorly through buildings, the system uses nearby transceivers that communicate directly with mobile devices via Wi-Fi. The RTT measurements are performed between mobile devices and these local transceivers, with the server calculating positions based on the measured distances and known transceiver locations, thereby achieving reliable indoor positioning
Data Source
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AI summary
Disclosed are systems, methods and devices for obtaining round trip time measurements for use in location based services. In particular implementations, a fine timing measurement request message wirelessly transmitted by a first transceiver device to a second transceiver device may permit additional processing features in computing or applying a signal round trip time measurement. Such a signal round trip time measurement may be used in positioning operations.