GRACE: A Hierarchical Adaptation Framework for Saving Energy

Mobile systems primarily processing multimedia data are expected to become important platforms for pervasive computing. These systems, however, must satisfy large, dynamic demands of multimedia applications subject to stringent energy, computational, and bandwidth constraints. At the same time, multimedia applications provide the possibility of \emph{adaptation}, allowing tradeoffs between energy, computation, and network bandwidth to maximize the user's experience for the current resources. Researchers have proposed adaptations in the hardware, network, operating system, and applications to provide QoS guarantees and to save energy. To reap the full benefits of such adaptations, however, the different system layers and applications must coordinate their adaptations with each other. This paper describes a framework, called \emph{GRACE}, to achieve such a coordination, using a novel hierarchical approach that combines global, per-application, and per-layer internal adaptation, for multimedia applications running on wireless systems. GRACE achieves the benefits of coordination through cleanly defined interfaces that keep the internals of the different layers isolated from each other. Our results so far show the effectiveness of the hierarchical adaptations, and justify the use of coordinated, cross-layer adaptations to both save energy and improve the user's multimedia experience