Mesh Network Clock Synchronization for Precise RF Asset Tracking
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Solution Overview
Problem
Existing location tracking technologies, such as GPS and Wi-Fi positioning, are ineffective indoors and in urban environments due to signal blocking and require extensive hardware infrastructure, limiting their accuracy and coverage, especially for applications requiring precision on the order of 1 meter or less.
Innovation Solution
A mesh network of RF transponders using time difference of arrival (TDoA) and multilateration (MLAT) for radiolocation, with a common reference clock, to track and locate RF transmitters, including mobile devices, by correlating demodulated signals and refining timing differences to determine precise locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS/GNSS is used for location tracking, then outdoor positioning accuracy is improved, but indoor and urban environment coverage deteriorates due to signal blocking
Solution Approach 1:
The patent introduces RF transponders as intermediary devices deployed in indoor and urban environments. These transponders act as local reference points that mediate between the blocked GPS signals and the target device, enabling positioning in environments where direct satellite signals are unavailable. The transponders create a local positioning infrastructure that complements GPS for seamless indoor-outdoor transition.
Solution Approach 2:
The patent replaces reliance on satellite-based electromagnetic signal propagation with a ground-based RF transponder network. Instead of depending on line-of-sight radio wave transmission from satellites through the atmosphere, the system uses localized RF transponders that generate and process signals within the target environment, eliminating the fundamental limitation of signal blocking by buildings and structures.
2Adaptability or versatility
If extensive hardware infrastructure is deployed to improve tracking coverage, then location availability is improved, but system complexity and cost increase
Solution Approach 1:
The RF transponders are designed to perform multiple functions: they serve as positioning reference points, provide timing synchronization via common reference clock, and can potentially serve as communication nodes. This multi-functionality reduces the need for separate specialized infrastructure components, thereby lowering overall system complexity while maintaining comprehensive tracking coverage.
Solution Approach 2:
The system uses TDoA (time difference of arrival) and FDoA (frequency difference of arrival) measurement techniques to achieve precise positioning without requiring dense hardware deployment. By changing the measurement parameters from direct distance measurement to time/frequency difference measurement, the system can achieve the same positioning accuracy with fewer transponders, reducing infrastructure complexity.
3Adaptability or versatility
If traditional radiolocation methods are used, then positioning capability is provided, but precision reaches only several meters instead of sub-meter accuracy
Solution Approach 1:
The system performs preliminary timing synchronization by establishing a common reference clock across all RF transponders before conducting TDoA measurements. This preliminary action of synchronizing the timing基准 eliminates timing drift and synchronization errors that would otherwise limit positioning accuracy to several meters, enabling sub-meter precision by ensuring all measurements are referenced to a unified time base.
Solution Approach 2:
The patent replaces conventional angle-of-arrival (AoA) measurement methods with TDoA/FDoA-based multilateration. By substituting directional antenna measurements with time and frequency difference measurements, the system achieves higher precision because time/frequency measurements can be made with greater accuracy than angular measurements, especially in multipath environments where signal reflections corrupt AoA data.
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
Enables accurate, cost-effective indoor and urban tracking of assets with precision down to 3 cm, robust against multipath propagation and interference, without the need for extensive hardware infrastructure.
Implementation Method 1
demodulating the transmitted signal at the first node to produce a demodulated local signal
Implementation Method 2
autocorrelating the demodulated local signal and the demodulated remote signal to recover first timing differences
Implementation Method 3
radiolocation of RF transmitters using time difference of arrival or frequency difference of arrival (TDoA/FDoA) and multilateration (MLAT)
Implementation Method 4
multilateration (MLAT) via a mesh network of RF transponders
Implementation Method 5
refining timing differences to determine precise locations
Data Source
AI summary
A method of determining a reference clock in a mesh network includes receiving multiple signals, correlating the multiple signals with a local signal generated by the first node to determine a coarse set of time differences, refining the coarse set of time differences using a phase of a carrier signal of the multiple signals to produce a refined set of time differences, and using the refined set of time differences to define a reference clock.