Analysis of CSI-based Human Activity Recognition for Contactless Patients Monitoring

Contactless patient monitoring is one of the most trending topics in eHealth, due to the utmost importance of non-invasive tele-enabled biomedical systems in next-generation healthcare. In this connection, this work investigates Human Activity Recognition (HAR) using commodity 5GHz WiFi devices, exploiting Channel State Information (CSI) to distinguish among a set of actions performed by different people. The position and movements of the human body affect wireless signal reflections and, consequently, CSI. Data collected from wireless packets are organized into the CSI matrix, which describes the status of the link at each time instant. In this work we employ amplitude and phase information, related to the variations in CSI values, to classify human activities leveraging simple machine learning techniques. Different radio link modes are also compared to evaluate their impact on the classification performance. Experimental results show that CSI data is capable of providing very accurate results in classifying activities performed by different people, especially when considering phase-related information in a multiple-input-multiple-output (MIMO) configuration, thus making CSI-based HAR a promising solution for contactless patient monitoring.