Time-Reversal Wireless Object Tracking in Multipath Environments
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Solution Overview
Problem
Existing indoor object tracking and speed estimation methods face challenges in accurately estimating low speeds, such as human walking speed, in rich-scattering environments due to interference from multipath signals and require line-of-sight conditions, leading to unsatisfactory accuracy and false alarms in motion detection systems.
Innovation Solution
A method utilizing time-reversal technology to extract spatial-temporal information from wireless multipath channels, processing time series of channel information to determine object movement characteristics like speed and direction, even in complex indoor environments without line-of-sight conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional Doppler effect methods are used for speed estimation, then the system can estimate speed, but the accuracy deteriorates for low speeds like human walking speed due to extremely small Doppler shifts
Solution Approach 1:
The patent replaces traditional Doppler-based mechanical measurement with time-reversal wireless communication technology. By transmitting signals through wireless channels and analyzing the time-reversed channel impulse response, the system can accurately measure spatial-temporal information including speed and direction without relying on small Doppler shifts, thus solving the low-speed detection accuracy problem.
Solution Approach 2:
The patent introduces wireless channel impulse response as an intermediary medium to transfer motion information. Instead of directly measuring small Doppler shifts, the system uses the time-reversed channel response as a mediator that contains enriched spatial-temporal information about object motion, enabling accurate low-speed detection through signal processing rather than direct physical measurement.
2Loss of time
If dead-reckoning method with IMU is used for location estimation, then the system can estimate location in real time, but the manufacturing precision and reliability deteriorate due to cumulative errors in moving distance estimation
Solution Approach 1:
The patent replaces mechanical IMU-based dead-reckoning with wireless signal-based time-reversal positioning. By analyzing the time-reversed channel impulse response from wireless signals, the system obtains accurate spatial-temporal information without the cumulative error problems of mechanical inertial measurement, thus improving location estimation precision while maintaining real-time capability.
Solution Approach 2:
The patent employs feedback mechanisms through the time-reversal process, where the channel impulse response is continuously updated based on the time-reversed signals. This feedback loop allows the system to correct and refine location estimates in real-time, compensating for errors and maintaining high precision without the drift problems of traditional dead-reckoning methods.
3Productivity
If traditional motion detection methods are used in rich-scattering environments, then the system can detect motion, but reliability deteriorates due to false alarms caused by multipath signal interference
Solution Approach 1:
The patent extracts and isolates the direct path component from the complex multipath signals by using time-reversal processing. By focusing analysis on the time-reversed channel impulse response, the system separates the useful direct path information containing true motion signals from the harmful multipath interference, enabling reliable motion detection in rich-scattering environments without false alarms.
Solution Approach 2:
The patent uses time-reversed channel impulse response as an intermediary that filters out multipath interference. This intermediary processing step transforms the complex multipath signals into a form where the direct path component is enhanced and multipath components are suppressed, thereby improving reliability by eliminating false alarms while maintaining motion detection productivity.
4Measurement precision
If line-of-sight conditions are required for accurate tracking, then the system can achieve good measurement precision, but adaptability deteriorates in complex indoor environments without line-of-sight
Solution Approach 1:
The patent replaces line-of-sight-based mechanical tracking with wireless time-reversal tracking that can operate in rich-scattering environments. By using wireless signals and time-reversal processing to extract spatial-temporal information from multipath components, the system achieves accurate tracking without requiring direct line-of-sight, thus improving environmental adaptability while maintaining measurement precision.
Solution Approach 2:
The patent changes the fundamental parameters of signal transmission and processing by using time-reversal techniques. This parameter change enables the system to exploit multipath components rather than requiring their elimination, allowing accurate tracking in environments without line-of-sight conditions while maintaining precision through enhanced signal processing capabilities.
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 enables accurate object tracking and speed estimation in rich-scattering environments, improving the reliability of motion detection and reducing false alarms by leveraging time-reversal technology to analyze wireless signals impacted by object movement.
Implementation Method 1
A method utilizing time-reversal technology to extract spatial-temporal information from wireless multipath channels
Implementation Method 2
wireless multipath channel impacted by a current movement of an object
Data Source
AI summary
Method, apparatus and systems for object tracking are disclosed. In one example, a system for tracking a plurality of objects in a venue is disclosed. The system comprises a transmitter configured for transmitting a series of probe signals in a broadcasting manner through a wireless multipath channel, wherein the wireless multipath channel is impacted by a movement of at least one of the plurality of objects in the venue; and a plurality of heterogeneous target wireless receivers each of which is associated with an object of the plurality of objects in the venue. Each of the plurality of heterogeneous target wireless receivers is configured for: receiving the series of probe signals through the wireless multipath channel between the heterogeneous target wireless receiver and the transmitter, obtaining at least one time series of channel information (TSCI) of the wireless multipath channel based on the series of probe signals received by the heterogeneous target wireless receiver, and tracking the object associated with the heterogeneous target wireless receiver based on the at least one TSCI.