Human Activity Recognition with Device-Free Sensors for Well-Being Assessment in Smart Homes

Human Activity Recognition (HAR) has attracted much attention in the last two decades with applications such as remote health monitoring, security and surveillance, and smart environments. Specifically, for well-being assessment, HAR systems give us the possibility of recognizing important physical activities in the patient's daily living. For instance, using motion sensors to monitor and record the physical situations and postures of patients with chronic conditions such as arthritis and cardiovascular disease which cause limitations in mobility can be useful in behavior assessment [1]. These physical records, especially for people with disabilities or elderly people, provide caregivers with useful information for treatment. Another example is fall detection that could notify caregivers instantly when a person falls. Today, many types of sensors are used for human activity recognition, including vision-based, wearable, object-tagged and device-free. In this article, we focus on device-free sensors and give and overview of their applications in HAR for well-being assessment in smart homes, including examples from the existing literature and our own test results for simple activity recognition with some of these sensors. We will see that device-free sensors are used predominantly for fall detection, although other well-being applications such as cognitive assessment, respiration monitoring, and dementia detection have emerged as well. Let us begin by looking at various types of HAR sensors and identifying the characteristics of each of them.