Wireless Localization Using Round-Trip Delay Correction
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Solution Overview
Problem
Existing wireless localization systems face inaccuracies due to radio propagation environments and hardware limitations, particularly in multipath environments where TOA-based techniques struggle with multipath reflections and require costly hardware for accurate direction determination.
Innovation Solution
A method for computing round trip delay between nodes, correcting for frequency offset and relative motion, and discarding error-prone range data to improve location estimation using TOA measurements, enabling more robust and accurate localization with low-cost hardware in large areas without the need for cabling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If TOA-based localisation is used in multipath environments, then location estimation can be performed, but accuracy deteriorates due to multipath reflections
Solution Approach 1:
The patent changes the parameter being measured from direct TOA to round-trip delay, which is less susceptible to multipath effects. By measuring the time for a signal to travel from node A to node B and back to node A, the system can identify and eliminate multipath reflections that don't follow the direct round-trip path, thereby improving location estimation accuracy in multipath environments.
Solution Approach 2:
The patent implements a feedback mechanism where nodes exchange timing information and measure round-trip delays to continuously refine synchronization and location estimates. The system uses the measured delays to adjust frequency offsets and correct timing errors, creating a closed-loop system that improves accuracy over time despite multipath interference.
2Measurement precision
If AOA techniques are used to determine direction of arrival, then location accuracy can be improved, but device complexity increases due to expensive hardware requirements
Solution Approach 1:
The patent replaces the mechanical/AOA hardware system (which would require expensive antenna arrays and complex signal processing) with a time-based measurement system. Instead of measuring angle of arrival using physical antenna configurations, the system uses round-trip time measurements and multilateration mathematics to determine location, achieving similar accuracy with much simpler, lower-cost hardware.
3Ease of operation
If wireless connections are used between anchor nodes to reduce installation complexity, then ease of deployment improves, but frequency and time synchronisation accuracy deteriorates
Solution Approach 1:
The patent uses feedback mechanisms where nodes continuously exchange timing information and measure round-trip delays to dynamically adjust for frequency offsets and synchronization errors. This closed-loop approach maintains synchronization accuracy despite the lack of hardwired connections, enabling wireless deployment without sacrificing measurement precision.
Solution Approach 2:
The patent changes from assuming perfect synchronization (which would require hardwired connections) to measuring and correcting round-trip delays that account for frequency offsets and timing errors. By transforming the problem from one of maintaining synchronization to one of measuring and compensating for desynchronization, the system enables wireless deployment while maintaining accuracy.
4Ease of operation
If round trip delay measurement is used to handle wireless connections, then ease of deployment improves, but measurement accuracy deteriorates due to frequency offsets and propagation delays
Solution Approach 1:
The patent implements feedback loops where nodes exchange timing information and use measured round-trip delays to continuously refine their frequency offset estimates and synchronization parameters. This iterative correction process compensates for the inaccuracies introduced by wireless propagation, maintaining measurement precision while enabling wireless deployment.
Solution Approach 2:
The patent transforms the round-trip delay measurement from a direct distance calculation into a basis for determining frequency offsets and synchronization parameters. By changing how the measurement is used - from directly computing distance to first characterizing the communication channel and then using that characterization for accurate location estimation - the system overcomes the precision deterioration caused by wireless propagation effects.
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
The solution enhances localization accuracy by correcting for frequency offsets and motion, discarding bad data, and using low-cost hardware, making it suitable for large areas and rapid deployment in various environments, including indoor settings.
Implementation Method 1
measurement of the time-of-arrival of radio signals between the nodes
Implementation Method 2
correcting for frequency offset and relative motion between the nodes
Data Source
AI summary
Disclosed is method of computing a round trip delay between a pair of nodes, the method comprising transmitting at least one beacon at a known transmit time from each of the nodes; measuring the times-of-arrival of the beacons at other of the nodes; and estimating a round trip delay between the nodes from the measured times-of-arrival and the transmit times; and correcting the round trip delay for either or both of a frequency offset between the nodes and relative motion between the nodes.