Indoor Wi-Fi Positioning Using Simultaneous FTM Burst Measurements
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Solution Overview
Problem
The Fine Timing Measurement (FTM) protocol in IEEE 802.11 for indoor locationing suffers from high power consumption, channel switching requirements, dense AP deployment needs, increased traffic load, and uncertainties due to TOF measurements at different time instances, leading to inefficient and slow system response.
Innovation Solution
Implementing a method that uses sensor STA/neighbor APs to exchange FTM frames, where listening devices measure and transfer timestamps to determine location efficiently, allowing for simultaneous TOF calculations with multiple APs during the same FTM frame exchange burst, reducing airtime and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If FTM protocol is used for indoor locationing with multiple APs, then positioning accuracy is improved, but power consumption increases
Solution Approach 1:
The patent combines multiple FTM measurement sessions into a single burst by having the initiating STA perform measurements with multiple APs simultaneously rather than sequentially. This merging approach maintains positioning accuracy while significantly reducing the total time the STA needs to be in active measurement mode, thereby lowering power consumption.
Solution Approach 2:
The patent implements a setup phase before the measurement phase where the initiating STA obtains information about sensor STAs or neighbor APs in advance. This preliminary action allows the STA to configure and prepare for efficient measurement sessions, reducing the time required for actual measurements and thus lowering power consumption while maintaining accuracy.
2Measurement precision
If FTM frame exchange with multiple APs is performed sequentially, then positioning can be achieved, but airtime increases
Solution Approach 1:
The patent merges multiple sequential FTM frame exchanges into a single burst by having the initiating STA conduct measurements with multiple APs simultaneously. This approach maintains the ability to achieve positioning through multiple AP measurements while dramatically reducing the total airtime required, as all measurements occur in parallel rather than one after another.
Solution Approach 2:
The patent transitions from a temporal dimension approach (sequential measurements over time) to a spatial dimension approach (simultaneous measurements with multiple APs). By utilizing multiple APs in different spatial locations for concurrent measurements, the system achieves positioning without increasing airtime, effectively adding a spatial dimension to the measurement process.
3Adaptability or versatility
If channel switching is required for each AP measurement, then measurements with different APs can be performed, but operation complexity increases
Solution Approach 1:
The patent performs channel information gathering during the setup phase before actual measurements begin. The initiating STA obtains channel information about sensor STAs or neighbor APs in advance, allowing it to pre-configure measurement parameters and avoid the need for dynamic channel switching during the measurement burst. This maintains measurement flexibility while significantly simplifying operation.
Solution Approach 2:
The patent introduces sensor STAs or neighbor APs as intermediaries that provide timing information without requiring direct communication between the initiating STA and all APs. These intermediaries facilitate the measurement process by providing timestamps that enable distance calculations, reducing the operational complexity of coordinating direct FTM exchanges with multiple APs on different channels.
4Adaptability or versatility
If TOF measurements are performed at different time instances, then positioning with multiple APs is possible, but measurement uncertainty increases
Solution Approach 1:
The patent merges multiple TOF measurements into a single simultaneous measurement burst where all APs are measured at the same time instance. This combining approach maintains the ability to position using multiple APs while eliminating the uncertainties that arise from measuring at different times, as all measurements are taken concurrently under identical temporal conditions.
Solution Approach 2:
The patent prepares and synchronizes the measurement process during the setup phase, establishing a coordinated measurement burst where all TOF measurements occur simultaneously. This preliminary coordination ensures that measurements are taken at the same time instance across all APs, eliminating temporal variations and associated uncertainties while maintaining positioning capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach simplifies indoor locationing operations, reduces airtime and power consumption, and facilitates easier deployment by enabling accurate and efficient distance calculations with multiple APs in a single FTM frame exchange, improving system response and reducing uncertainties.
Implementation Method 1
ranging using time-of-flight (TOF) ranging measurements defined in IEEE 802.11v. Once the distance between devices is measured, the information can be used to determine device location.
Implementation Method 2
an initiating station exchanges FTM frames with a responding station to measure the time-of-flight (TOF) or the Round Trip Delay (RTD/2)
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
A method of a ranging and positioning with sensor STA/neighbor AP is proposed. An initiating wireless device establishes an FTM procedure with a responding wireless device in an indoor wireless local area network. The initiating device exchanges FTM frames with the responding device and thereby receiving a first set of timestamps from the responding device. The initiating device receives a second set of timestamps associated with the exchanged FTM frames from one or more listening devices. Finally, the initiating device determines location information from the first and the second set of timestamps.