A Butterworth low-pass filter is a signal processing filter designed to pass low-frequency components of a signal while attenuating high-frequency noise, characterized by a maximally flat frequency response in the passband with no ripple. In WiFi CSI sensing, it is applied to raw CSI amplitude and phase streams to suppress high-frequency environmental noise and hardware-induced fluctuations, thereby preserving the slower, motion-related signal variations that are critical for accurate gesture recognition and other sensing tasks. The filter is commonly parameterized by its order and cutoff frequency, with higher-order variants providing steeper roll-off at the cost of increased computational complexity, and it is typically implemented as a zero-phase filter to avoid introducing phase distortion into the already noise-sensitive CSI measurements.
Source Papers
- CSI-Chain: A Complete End-to-End Framework for WiFi CSI Sensing ↗ — CSI-Chain: A Complete End-to-End Framework for WiFi CSI Sens
- Device-Free Wireless Sensing for Gesture Recognition Based on Complementary CSI Amplitude and Phase ↗ — Device-Free Wireless Sensing for Gesture Recognition Based o
- Understanding and Modeling of WiFi Signal Based Human Activity Recognition ↗ — Understanding and Modeling of WiFi Signal Based Human Activi