Mobile
Computing
Mobile Computing At Duke
Milly Watt Project
Milly Watt Project
Mobile computing is dramatically changing our day-to-day lives, especially with the popularity of small devices such as personal digital assistants (PDAs) and with the embedding of substantial processing capabilities in devices such as telephones and cameras. Reducing the energy consumed in using these devices, thereby extending the lifetime of the batteries that power them (and reducing the weight of carrying spares), is one of the major challenges in designing such systems. Power consumption is an issue that extends well beyond the realm of battery-powered mobile devices to any computing platform in which heat or fan noise production may be factors (e.g. medical applications). Finally, energy efficiency of computers is desirable in its own right from both the economic and environmental points of view.
This problem can be addressed at various levels: by improving battery technology, by engineering more efficient electronics and components, and by designing computer architectures and software with power as a primary measure of performance. Power is a critical, limited, and shared system resource. Traditionally, the operating system plays a major role in managing such resources. We also believe that the applications hold an important key, in the application-specific constraints and opportunities for saving energy that can be known only at that level. Therefore, our approach is to have the needs of the applications be the driving force for the development of power management functions in the operating system and of a power-based API that allows a partnership between applications and the system in setting energy use policy.
Quality Aware Transcoding
Quality Aware Transcoding
The primary focus of this research is in enabling multimedia web access from slow, expensive and congested networks using application level techniques. We utilize transcoding as the enabling technology. Transcoding is a transformation that is used to convert a multimedia object from one form to another (frequently trading off object fidelity for size). For transcoding to be useful, we need to understand the tradeoff characteristics: the information quality loss, the computational overhead required in computing the transcoding and the potential space benefits. To illustrate for one specific case, we characterized the information quality tradeoffs, the computational requirements and the potential space gain of a transcoding that changes the JPEG compression metric. We utilized this technology in a network proxy service that serves different versions of the images to different client based on their network characteristics. Next we utilized this technology in a web service that utilizes Quality Aware transcoding to manage its available bandwidth and provide differentiated QoS depending on the client
Hiker's Buddy (1997-98)
Hiker's
Buddy
The goal of this project is to develop a particular application for the PalmPilot as a research vehicle for understanding the issues behind adaptability and the requirements for system software that will support the design of such adaptable applications. The "Hiker's Buddy" design combines GPS positioning with topo maps and wireless communication back to a "homebase" machine to explore not only the mountains of the Pacific Northwest (while I was on sabbatical), but also to explore a very rich "variability space" involving battery life (of both the Pilot and GPS receiver), satellite accessibility, map complexity, route deviations, and wireless connectivity. The experience of building this application helps identify the desired functionality for a systems framework to support development of such mobile applications.
