In this paper we show that application-aware adaptation, a collaborative partnership between the operating system and applications, offers the most general and effective approach to mobile information access. We describe the design of Odyssey, a prototype implementing this approach, and show how it supports concurrent execution of diverse mobile ap-plications. We identify agility as a key attribute of adap-tive systems, and describe how to quantify and measure it. We present the results of our evaluation of Odyssey, indi-cating performance improvements up to a factor of 5 on a benchmark of three applications concurrently using remote services over a network with highly variable bandwidth. 1

Subjecting a mobile computing system to wireless network conditions that are realistic yet reproducible is a challenging problem. In this paper, we describe a technique called trace modulation that re-creates the observed end-to-end characteristics of a real wireless network in a controlled and repeatable manner. Trace modulation is transparent to applications and accounts for all network traffic sent or received by the system under test. We present results that show that it is indeed capable of reproducing wireless network performance faithfully. 1 Introduction How does one subject a mobile computing system to realistic yet reproducible wireless networking conditions? Reproducible behavior is important for three reasons. First, it is essential for thorough evaluation of the performance of a mobile computing system. Second, it is necessary for comparative evaluations of alternative system designs. Third, it is valuable in debugging mobile systems because it enables the re-creation of...

We describe a novel on-line file access predictor, Recent Popularity, capable of rapid adaptation to workload changes while simultaneously predicting more events with greater accuracy than prior efforts. We distinguish the goal of predicting the most events accurately from the goal of offering the most accurate predictions (when declining to offer a prediction is acceptable). For this purpose we present two distinct measures of accuracy, general and specific accuracy, corresponding to these goals. We describe how our new predictor and an earlier effort, Noah, can trade the number of events predicted for prediction accuracy by modifying simple parameters. When prediction accuracy is strictly more important than the number of predictions offered, trace-based evaluation demonstrates error rates as low as 2%, while offering predictions for more than 60% of all file access events.

Mobile devices and wireless networks are becoming more powerful and affordable, leading to the growing importance of mobile data access. Unfortunately, mobile environments are inherently turbulent; the resources available to mobile clients change dramatically and unpredictably over time. This dissertation puts forth the claim that clients must adapt their behavior to such turbulence by trading quality of fetched data for performance in fetching it. Such adaptation is best provided by application-aware adaptation --- a collaboration between the operating system and its applications. In this collaboration, the system is responsible for providing the mechanisms for adaptation, while applications are free to set adaptive policies. The dissertation next describes the design and implementation of Odyssey, a platform for mobile data access. This discussion focuses on the mechanisms provided by the system, the architecture comprising those mechanisms, and the application programming interface ...