Characterizing, modeling, and improving the QoE of mobile devices with low battery level

Mobile users always require an excellent user experience which is the top challenge faced by today's mobile device designers and producers. Mobile devices are battery constrained, thus developing energy-saving techniques to extend the battery life is critical in terms of the user experience. Since the discrepancy between the device energy and battery energy consumption is becoming large when the battery is approaching to depleted, the battery energy-savings mechanisms (instead of the previously explored device energy-saving mechanisms) that target at the low battery level are highly desirable. Besides the battery life, mobile users demand a good system responsiveness, which is also an essential component in the user experience. In this paper, we mainly focus on the mobile devices with the low battery level. We first introduce the concept of Quality of Experience (QoE), which quantitatively combines the two major factors (i.e., the battery life, and performance) into an integrated metric. We then characterize the QoE by capturing various users' psychological changes during the low battery phase, which affect the users' preference on battery life or performance. We further explore a QoE model that includes the online battery and performance models. Finally, we propose a QoE-aware frequency governor which dynamically changes the CPU frequency to achieve the optimal QoE at the low battery phase for different users at different environments. Our experiment results show that our QoE-aware frequency governor improves the QoE significantly.