Energy-Efficient Daily Human Activity Logging Platform on Smart Mobile Devices

Abstract

Nowadays, recording a personal life log (PLL) of daily human activities plays an important role in wellness-care and context-aware systems. Human activities, one of the most important information in PPL, can be recognized in real-time by using sensory data collected from various sensors built in smart mobile devices. Recent studies have focused on human activity recognition (HAR) that is solely based on triaxial accelerometers, which is the most energy-efficient approach. However, such HAR approaches are still energy-inefficient because the accelerometer is required to run without stopping so that the physical activity of a user can be recognized in real-time. In this paper, we propose a novel approach for HAR process that controls the activity recognition duration for energy-efficient HAR. We investigated the impact of varying the acceleration-sampling frequency and window size for HAR by using the variable activity recognition duration (VARD) strategy. Our PLL platform exhibits three main modules: energy-efficient HAR, activity information generation (AIG), and PLL database. Upon the recognition of each activity, AIG module estimates activity information that includes energy expenditure based on metabolic equivalents, stride length, step count, moving distance, and moving speed. Our platform operates real-time, and the PLL information it generates is archived in a PLL database. We implemented our approach by using an Android platform and evaluated its performance in terms of energy efficiency and accuracy. The experimental results showed that our HAR approach reduced energy consumption by a minimum of about 44.23% and maximum of about 78.85% compared to conventional HAR without sacrificing accuracy and that our AIG approach archives the activity information’s average difference of about 5% compared to ground truth. Our results demonstrate the feasibility of energy-efficient daily human activity logging system that could be used for u-health and wellness-care services in the near future.