An accurate two-tier classifier for efficient duty-cycling of smartphone activity recognition systems

  • Authors:
  • Vijay Srinivasan;Thomas Phan

  • Affiliations:
  • Samsung R&D Center, San Jose, CA;Samsung R&D Center, San Jose, CA

  • Venue:
  • Proceedings of the Third International Workshop on Sensing Applications on Mobile Phones
  • Year:
  • 2012

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Abstract

Our vision is a smartphone service that accurately tracks users' physical activities and transportation modes using accelerometer-based activity recognition carried out on the phone. A key challenge that needs to be addressed to realize this vision is the high power consumption of keeping the smartphone awake in order to perform sensor sampling, feature extraction, and activity classification. In this paper, we propose a two-tier classifier for reducing the wake time percentage of the activity recognition system, which we define as the percentage of time the activity recognition system keeps the smartphone awake. We compare our two-tier classifier to (i) a conventional single-tier classifier, and (ii) a confidence-based multi-tier classifier designed to reduce wake time. We evaluate our approaches using activity-labeled smartphone accelerometer data traces from 2 subjects over a total of 60 hours performing 7 different physical activities. Given an accuracy lower bound of 91%, our two-tier approach achieves the lowest wake times and is able to reduce the wake time percentage of the best single-tier classifier by 93.0% and 70.1% respectively for the 2 subjects.