Department of Computer Science and Information Engineering and 
IEEE Gainesville Section Presents 

Cross-Layer Adaptation for Quality-Aware and Energy-Efficient Next 
Generation Mobile Multimedia Devices


Klara Nahrstedt, Fisher Professor 
Department of Computer Science
University of Illinois at Urbana-Champaign

Place: CSE Building Room E404 
Time:  4:00-5:00pm, Wednesday, March 17 

Abstract

Mobile systems primarily processing multimedia data are expected to become 
a dominant computing platform for a variety of application domains. The 
design of such systems imposes several new challenges, as it must consider 
demanding, dynamic and multi-dimensional resource requirements and 
constraints, with energy becoming a first-class resource. At the same time, 
the ability of multimedia applications to trade-off output quality for 
system resources and the difference between their peak and average demands 
offers a huge opportunity for optimization. 

A promising approach to meet the challenges of systems in next generation 
mobile devices, therefore is to design all system layers with the ability to 
adapt in response to system or application changes. Furthermore, to get the 
full benefits of these adaptations, we argue that all system layers must 
cooperate to reach a system-wide globally optimal configuration. 

We have designed such coordinated and cross-layer adaptation framework, 
called GRACE, that integrates and coordinates the frequency/voltage scaling, 
soft-real-time scheduling (via GRACE-OS), and application quality adaptation. 
GRACE seeks first to maximize the system utility (i.e., the overall 
perceptual quality of applications) and then to save CPU energy.  To achieve 
these goals efficiently, GRACE uses a novel hierarchy of global, 
per-application, and internal adaptations, balancing the application benefits 
and cost. We have implemented the first version of GRACE  and evaluated it 
with adaptive AMD processor and multimedia video codecs such as MPEG decoder 
and H263 encoder. Our experimental results indicate that GRACE can increase 
system utility up to 98% and save energy up to 95% depending on workload and 
compared to previous systems adapting only some of the layers or not 
adapting at all. 
  


Brief Biography 

Klara  Nahrstedt  is a Fisher  Associate  Professor  at  the  University  
of Illinois at Urbana-Champaign,  Computer Science  Department.   Her 
research interests are directed   towards multimedia systems and networks, 
quality of service (QoS) routing, QoS and  resource management for 
distributed multimedia  systems over wire-line and wireless networks, and 
multimedia operating systems. She is the coauthor of the widely used 
multimedia book `Multimedia: Computing, Communications and Applications'  
published by Prentice Hall, the recipient of the Early NSF Career Award, 
the Junior Xerox Award, and the  IEEE Communication Society Leonard Abraham 
Award for Research Achievements. She is the editor-in-chief of the 
ACM/Springer  Multimedia Systems Journal, and the Ralph and Catherine 
Fisher Associate Professor.