Wi-Fi Radar Motion Detection via Echo Interpolation
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Solution Overview
Problem
Existing Wi-Fi access points struggle to effectively detect human motion due to small radar cross-section and low Doppler shifts, often masked by stronger reflections from surroundings, and gaps in transmission sequences hinder accurate Doppler signature analysis.
Innovation Solution
Interpolate missing echo packets to reconstruct equally spaced sequences, enabling accurate Doppler shift estimation and human detection by synchronizing Wi-Fi signals for radar sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Wi-Fi access points use standard transmission sequences for communication, then communication functionality is maintained, but gaps in transmission sequences prevent accurate Doppler signature analysis for human motion detection
Solution Approach 1:
The system performs preliminary synchronization by recording timing information of transmitted packets and their corresponding echoes before processing. This preliminary timing record allows the system to later identify and fill gaps in the transmission sequence, ensuring continuous Doppler analysis capability even when standard communication protocols create transmission gaps
Solution Approach 2:
The system creates synthetic echo packets by interpolating between actual received echo packets. These synthetic copies fill in the missing data from gap periods, reconstructing a complete Doppler signature sequence that enables accurate human motion detection despite interruptions in the original transmission sequence
2Adaptability or versatility
If Wi-Fi signals are used for radar sensing, then human motion detection capability is added, but small radar cross-section and low Doppler shifts of human bodies make detection difficult against stronger surrounding reflections
Solution Approach 1:
The system extracts the Doppler shift information from the received echo packets by comparing the frequency of transmitted and received signals. This extraction process isolates the human motion signal from the stronger surrounding reflections, enabling precise detection despite the small radar cross-section of human bodies
Solution Approach 2:
The system uses the timing-synchronization signal and recorded timing information as feedback to identify gaps in the echo packet sequence. This feedback mechanism enables the system to request retransmission or generate synthetic packets to fill gaps, thereby maintaining continuous and precise Doppler signature analysis for accurate human motion detection
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
Enhances Wi-Fi access points' ability to detect human motion by overcoming gaps in transmission sequences, allowing for precise Doppler signature analysis and continuous radar sensing.
Implementation Method 1
The WLAN receiver is configured to receive the timing-synchronization signal from the WLAN transmitter over an internal interface, and to time-synchronize the echo packets and the corresponding WLAN packets using the timing-synchronization signal
Implementation Method 2
measuring a time delay between the echo packet and the direct leakage, and (c) estimating the distance based on the time delay
Implementation Method 3
Techniques that utilize wireless communication signals to identify human motion based on reflection of the wireless signals from the human body
Data Source
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AI summary
A Wireless Local-Area Network (WLAN) access point (20) includes a WLAN transmitter (24), a WLAN receiver (30), and a processor (11). The WLAN transmitter is configured to transmit WLAN packets and to send a timing-synchronization signal. The WLAN receiver is configured to receive echo packets including reflections from an object of the transmitted WLAN packets, to receive the timing-synchronization signal, and to time- synchronize the echo packets and the corresponding WLAN packets. The processor is configured to (a) in response to a gap in the received echo packets, generate one or more synthetic echo packets by interpolating over two or more of the time-synchronized received echo packets, to consequently derive a sequence of equally-spaced echo packets, (b) using the derived sequence of equally-spaced echo packets and the WLAN packets estimate one or more parameters of the object, and (c) output the estimated parameters to a user.