Extremely Low-resolution RFID Vision for Real-time and Visually-anonymized Action Recognition
Hyeonho Shin, Seungwoo Shim, Myeongkyun Cho, Youngki Lee, Jinwoo Shin, Song Min Kim · ACM Transactions on Sensor Networks · 2025
Despite the potential of vision-based personal monitoring (e.g., healthcare), private data leakage concerns hinder its wide deployment in personal spaces (e.g., bedrooms). A body of data anonymization designs was proposed throughout image processing and federated learning. They commonly store high-quality images and videos locally, which are anonymized via post-processing before cloud upload. However, the recent IoT camera hacking and local data leakage call for anonymized data at the sensing stage. Also, continuous and pervasive monitoring without blind spots in complicated indoor spaces requires a scalable and economic system. This article presents Mosaic , a vision-based end-to-end action recognition framework that (i) intrinsically achieves data anonymity from the sensing stage and (ii) battery-free operation for blind spot-free continuous monitoring. Mosaic leverages an extremely low resolution (eLR) Near-Infrared (NIR) image sensor with 6 \(\times\) 10 pixels for video anonymity and an RFID-compliant fully-passive tag with four solar cells for real-time eLR video streaming under as low as 30 lux (e.g., deep in the shelf without direct light). This is accompanied by a lightweight action recognition neural network for real-time inference (18.4 ms on Intel(R) Core i7-8700). Mosaic achieves an average of 98% accuracy on 10 action classes, hitting the balance between data anonymity and high-precision action recognition. Taking advantage of the NIR (non-visible) frequency, Mosaic also works in the dark without disturbing sleep. Lastly, wildfire detection reaching 20 m was demonstrated, showcasing the potential for outdoor monitoring.