Fresnel Zone-Based Voting With Capsule Networks for Human Activity Recognition From Channel State Information

Wireless local-area network (WLAN) sensing offers advantages over other approaches to human activity recognition (HAR) for Internet of Things (IoT) applications, including privacy as well as adaptability to non-line-of-sight scenarios. This is why HAR plays an important role in the upcoming IEEE 802.11bf Wi-Fi standard, which aims to bring the adoption of WLAN sensing to a much larger scale. In this paper, we propose CapsHAR, a model based on capsule networks, which uses channel state information (CSI) from Wi-Fi signals to accurately perform human activity recognition. We evaluate the capability of the model on a variety of datasets, including large and small-scale gestures, as well as compare its performance to a variety of models and approaches. We then extend the CapsHAR model into a distributed architecture in order to eliminate the communication overhead of sending CSI data from multiple access points (AP) to a single server. We propose the use of edge computing to run CapsHAR at each AP separately, then combine the outputs of the models through a Fresnel zone-based voting scheme which makes more efficient use of spatial diversity. Overall, the CapsHAR architecture consistently achieves classification accuracy surpassing that of the state-of-the-art models, demonstrating the viability of capsule networks for reliable HAR in Wi-Fi-based IoT applications.