Bio-Inspired Events and WiFi for Privacy Preserving HAR: A Large-scale Dataset and Novel Approach

Human Activity Recognition (HAR) supports applications ranging from healthcare monitoring to human-robot interaction. Existing HAR methods predominantly fuse RGB cameras and WiFi signals. However, RGB cameras raise privacy concerns, introduce redundancy, and degrade in low-light or occluded scenes, while WiFi lacks the spatial resolution to resolve fine-grained motion. Bio-inspired event cameras capture sparse brightness changes with high temporal resolution and reduced appearance detail, motivating a central research question: How can asynchronous event streams be effectively integrated with heterogeneous wireless signals to achieve robust and privacy-preserving HAR under real-world conditions? To investigate this question, we introduce ExWACT, the first large-scale event-WiFi HAR dataset, comprising 22.5K paired samples across 6 scenes in challenging simulated and real-world scenarios. By pairing complementary event streams and WiFi CSI, ExWACT enables systematic evaluation of multimodal fusion under diverse sensing conditions and investigation of domain shifts between simulated and real event data. Based on the dataset, we propose a novel temporally consistent fusion framework. Our key idea is to bridge the modality gap between dense wireless signals and sparse, asynchronous event streams via event-WiFi interaction and temporal alignment. The framework comprises two components. A Sparse Dual-branch Modality Encoder extracts motion-sensitive representations tailored to WiFi CSI and event streams. A Temporally Consistent Bi-directional Fusion (TCBF) module enables dynamic interaction between WiFi and events to capture latent spatial-temporal cues while enforcing temporal alignment. This design maintains high HAR accuracy and robustness under challenging visual conditions where traditional RGB-WiFi systems fail. Extensive experiments demonstrate that our method significantly outperforms pure WiFi baselines by +45.48% and existing fusion strategies by +13.65%. ExWACT establishes a new direction for privacy-preserving HAR, bridging wireless WiFi and bio-inspired sensing and laying a solid foundation for further research on real-world HAR.