E-eyes

TLDR

Activity monitoring in home environments is increasingly important for elder care, well‑being management, and child safety. This paper proposes device‑free, location‑oriented activity identification at home using existing WiFi access points and devices. A low‑cost system exploits the complex web of WiFi links and fine‑grained channel state information to extract channel features, build semi‑supervised signal profiles, and uniquely identify in‑place activities and walking movements. Experimental evaluation in two apartments shows over 96 % true‑positive and less than 1 % false‑positive rates with a single WiFi access point, and higher accuracy with 802.11ac.

Abstract

Activity monitoring in home environments has become increasingly important and has the potential to support a broad array of applications including elder care, well-being management, and latchkey child safety. Traditional approaches involve wearable sensors and specialized hardware installations. This paper presents device-free location-oriented activity identification at home through the use of existing WiFi access points and WiFi devices (e.g., desktops, thermostats, refrigerators, smartTVs, laptops). Our low-cost system takes advantage of the ever more complex web of WiFi links between such devices and the increasingly fine-grained channel state information that can be extracted from such links. It examines channel features and can uniquely identify both in-place activities and walking movements across a home by comparing them against signal profiles. Signal profiles construction can be semi-supervised and the profiles can be adaptively updated to accommodate the movement of the mobile devices and day-to-day signal calibration. Our experimental evaluation in two apartments of different size demonstrates that our approach can achieve over 96% average true positive rate and less than 1% average false positive rate to distinguish a set of in-place and walking activities with only a single WiFi access point. Our prototype also shows that our system can work with wider signal band (802.11ac) with even higher accuracy.