Design and evaluation of a cross-layer adaptation framework for mobile multimedia systems

Mobile multimedia systems must provide application quality of service (QoS) in the presence of dynamically varying and multiple resource constraints (e.g., variations in available CPU time, energy, and bandwidth). Researchers have therefore proposed adaptive systems that can respond to changing resource availability and application demands. All system layers can benefit from adaptation, but fully exploiting these benefits requires a new cross-layer adaptation framework to coordinate the adaptations in the different layers. This paper presents such a framework and its first prototype, called GRACE-1. The framework supports application QoS under CPU and energy constraints via coordinated adaptation in the hardware, OS, and application layers. Specifically, GRACE-1 uses global adaptation to handle large and long-term variations, setting application QoS, CPU allocation, and CPU frequency/voltage to qualitatively new levels. In response to small and temporary variations, it uses local adaptation within each layer. We have implemented the GRACE-1 prototype on a laptop system with an adaptive processor. Our experimental results show that, compared to previous approaches that exploit adaptation in only some of the layers or in an uncoordinated way, GRACE-1 can provide higher overall system utility in several cases.