WiFi Channel Information for Fall Detection
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Solution Overview
Problem
Current indoor motion tracking and speed estimation methods, particularly for human walking speed, face challenges in accuracy due to the small Doppler shift and interference from multipath signals in complex indoor environments, and existing systems struggle with transient motions like falls in non-line-of-sight conditions.
Innovation Solution
A system utilizing time-reversal technology to monitor transient motions by analyzing a time series of channel information from wireless multipath channels, enabling accurate speed estimation and detection of events like falls without the need for line-of-sight conditions, using standard WiFi chips for wide availability and affordability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Doppler effect is used for speed estimation, then speed can be estimated, but the accuracy deteriorates due to small Doppler shift at low speeds and multipath interference in indoor environments
Solution Approach 1:
The patent extracts and focuses on the Time of Arrival (TOA) component from the wireless signal characteristics, separating it from the problematic Doppler shift-based approaches. By using TOA of direct and reflected signals, the system can estimate speed without being affected by small Doppler shifts at low speeds or multipath interference, directly addressing the accuracy deterioration issue.
Solution Approach 2:
The patent introduces TOA as an intermediary parameter to bridge the gap between wireless signal transmission and speed estimation. Instead of directly measuring Doppler shift, the system uses TOA differences of signals traveling through different paths (direct and reflected) to calculate speed, thereby avoiding the harmful effects of multipath interference on the measurement accuracy.
2Measurement precision
If line-of-sight conditions are required for accurate detection, then detection accuracy improves, but the system becomes inapplicable in complex indoor environments without line-of-sight
Solution Approach 1:
The patent makes the detection system universal by enabling it to function in both line-of-sight and non-line-of-sight conditions. By using TOA differences that can be extracted from multipath signals, the system can accurately detect transient motions regardless of whether direct line-of-sight exists, thereby improving adaptability to various indoor environments while maintaining detection accuracy.
Solution Approach 2:
The patent converts the harmful multipath interference into a beneficial resource for detection. Instead of treating multipath signals as noise to be eliminated, the system uses the TOA information from these reflected signals to detect transient motions, thereby turning the previously harmful factor into a useful measurement basis for improving detection capability in non-line-of-sight conditions.
3Reliability
If existing motion tracking methods are used, then motion can be tracked, but the system fails to accurately detect transient motions like falls in complex indoor environments
Solution Approach 1:
The patent applies dynamics by using the temporal variation of TOA differences to detect transient motions. The system monitors changes in TOA over time and uses the rate of change (derivative) to identify dynamic events such as falls. This dynamic approach enables reliable detection of transient motions while maintaining precision in speed estimation, as the TOA-based measurements capture the actual motion characteristics without the limitations of static or low-frequency methods.
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 system achieves high accuracy in detecting transient motions and speed estimation, including falls, in complex indoor environments, using off-the-shelf WiFi technology, and can monitor sleep stages and breathing rates with high precision, outperforming existing solutions.
Implementation Method 1
A system utilizing time-reversal technology to monitor transient motions by analyzing a time series of channel information from wireless multipath channels
Implementation Method 2
The Doppler effect has been widely applied to different speed estimation systems using sound wave, microwave, or laser light
Data Source
AI summary
Apparatus, systems and methods for detecting and monitoring fall-down actions and other transient motions are disclosed. In one example, a system for monitoring a transient motion in a venue is disclosed. The system comprises a transmitter, a receiver, and a transient motion monitor. The transmitter is located at a first position in the venue for transmitting a wireless signal through a wireless multipath channel impacted by the transient motion of an object in the venue. The receiver is located at a second position in the venue for: receiving the wireless signal through the wireless multipath channel, and obtaining a time series of channel information (CI) of the wireless multipath channel based on the wireless signal. The transient motion monitor is configured for: monitoring the transient motion based on the time series of CI, and triggering a response action based on the monitored transient motion.