Computing and Information Systems - Theses

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Start date: 2010 × End date: 2018 × Type: Masters Research thesis × Subject: activity recognition ×

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    Low-cost leaving home activity recognition using mobile sensing
    Li, Han ( 2017)
    Leaving home activity recognition (LHAR) is essential in context-aware applications. For example, on a rainy day, a smartphone can remind a user to bring an umbrella when the leaving home activity is recognized. However, research in this field is substantially lacking. Most existing studies require extra hardware such as sensors installed at home to help recognize such activities, which limits the applicability of these studies. With the ubiquity of mobile sensing technique, it becomes feasible for a smartphone to sense the ambient environment and a user’s current context. In this thesis, we develop a low-cost system using mobile sensing for timely recognition of leaving home activities. To the best of our knowledge, we are the first to recognize leaving home activities using only sensors on smartphones. Overall, our system can recognize leaving home activities within 20 seconds after the home door is closed with a precision of 93.1\% and recall of 100\%. Recognizing leaving home activities while only leveraging sensors on smartphones can be challenging in two aspects: 1) the diversity of home environments result in inconsistent features, which significantly affects the recognition performance; and 2) mobile sensing is restricted by limited resources on smartphones, e.g., power and computation capability. To overcome such limitations, we first investigate sensors available on commodity smartphones and find that features extracted from WiFi, barometer, cell tower, magnetic field sensor and accelerometer readings are relatively robust in recognizing leaving home activities. Second, due to the variety of residential property environments, we propose a sensor selection algorithm to adaptively select the most suitable sensors for each home to personalize the training. Both classification performance and sensing cost are taken into consideration to provide the user an option to trade power consumption for recognition accuracy, and vice versa. Inspired by the observation that leaving home activity usually involves walking, we activate the power-hungry sensors to start the recognition only when the walking event is detected. Thus, we reduce the sensing cost by 76.65\%.