Applying of Quality of Experience to system optimisation

State-of-the-art mobile devices, such as smart-phones and tablets, are highly versatile and must deliver high performance across a multitude of applications. The perceived performance and resulting user experience can make or break a design. It is therefore vital that device design and optimisation take into account the expectations and perceptions of the end user, as well as the types and requirements of the applications running on the device. Traditionally, device optimisation focuses on low-level metrics, such as CPU floating point performance or GPU frame rate, rather than on the aspects most important to the end user. In this work, we investigate the applicability of Quality of Experience (QoE) to system optimisation. We define a set of measurable QoE metrics, and run a set of experiments around a web browser and two graphics benchmarks. Using the results of these experiments, we show the advantages of using QoE as an optimisation metric by demonstrating the ability to optimally trade CPU performance for energy usage whilst taking into account the user experience. We investigate two GPU benchmarks to determine the ideal number of cores for energy efficiency, whilst ensuring a sufficiently high frame rate to maintain a high-quality user experience. We then look at the system as a whole, and the feasibility of using QoE to optimise performance and power consumption for the complete system, without sacrificing user experience. We achieve up to 60% savings in system energy usage with limited impact on the user experience.