On Energy, Adaptation, and the Death of Frames
Albert F. Harris, Robin Snader, Robin Hillary Kravets · Illinois Digital Environment for Access to Learning and Scholarship (University of Illinois at Urbana-Champaign) · 2006
Increases in computing capabilities of mobile devices have led to the use of multimedia applications that have high pro-cessor and bandwidth resource requirements, each of which consume significant energy. However, battery capacities have not kept pace, driving the design of energy-aware applica-tions. Traditionally multimedia applications have used en-coding techniques to deal with bandwidth constraints, es-sentially trading off CPU for networking resources. How-ever, in the context of energy constraints, it is not clear that this CPU-intensive approach is the most efficient. Making correct trade off decisions requires information about costs of both the CPU and the network. In addition to energy-savings by adaptive applications, further energy conserva-tion can be achieved by leveraging application layer informa-tion at the network layer. Because of their ability to tolerate loss, multimedia applications present unique opportunities to the design of such energy-efficient network protocols, de-spite their strict timing constraints. Essentially, transport protocols can use application level information to make in-telligent decisions about when to perform frame recovery, positively impacting system energy conservation. Previous adaptive systems concentrate on sharing resource informa-tion between the application and the network in only one direction and so perform sub-optimally. Therefore, it is nec-essary to design cooperative solutions that share resource information in both directions. To this end, we present a data-oriented energy model that exposes cross-layer inter-actions and enables specific optimizations in the applica-tion and network layers. We demonstrate that by passing a minimal amount of information in both directions, an adap-tive application paired with our adaptive transport proto-col, Reaper, can achieve significant energy savings, which we verify through a system implementation. 1.