Using Psychophysics to Guide Power Adaptation for Input Methods on Mobile Architectures

The predominant user activities on mobile architectures (e.g., smartphones) involve entering text in instant messaging apps, short message services, and social networking services. Recent research reveals that the normal use of input methods drains approximately half of the battery capacity due to their above-average power requirements and frequent use. In this paper, we first study the power characteristics of mobile input methods and find that they consistently over-provision resources to satisfy users. For example, the psychophysical evidence available indicates the response of spell-checking features within a time threshold makes users feel they have instant feedback. However, current systems perform it very quickly, which is imperceptible to users and costly in terms of energy use. Given this over- provisioning, the system can be slowed down to save energy while retaining the feeling of instant response. Inspired by this observation, we also exploit several other psychophysical facts to identify the exact criteria to satisfy users. As a result, we present a user experience-oriented technology, utexia, to optimize the energy use of mobile input methods. The evaluation shows that utexia conserves up to 42.9% in energy use while strictly ensuring a good user experience.