1. KAIS T System Support for Mobile, Adaptive Applications 2003. 4.8 Brian Noble, University of Michigan Presented by Hyeeun Choi

2. 2 / 9 System Support for Mobile, Adaptive Applications Contents Introduction Application Vs. OS Fidelity Agility Stability Future Work Conclusion

3. 3 / 9 System Support for Mobile, Adaptive Applications Introduction Difficulty of pervasive networking Quality of network connectivity afforded mobile users is extremely turbulent Mobile application must deal with such fluctuation How can deal with such fluctuation? Ideal Take advantage of high–quality connectivity Behave reasonably with poor performance What to do To monitor and control resource To make adaptive decision

4. 4 / 9 System Support for Mobile, Adaptive Applications Application Vs. OS Application-Aware Adaptation Odyssey’s approach : Collaborative Model Policy decision to Application Resource control to Operating System Application-aware collaboration Application-transparent System Laissez-faire application Each application must infer the resource consumption of the others. Without a common point of resource control, cannot have accurate knowledge of one another The OS on the mobile node is wholly responsible for making adaptation decisions for applications. Applications cannot choose to make their own adaptive decisions

5. 5 / 9 System Support for Mobile, Adaptive Applications Architecture of Adaptive Client Viceroy Manage type independent task on client Resource usage/availability monitoring Notifying application of changes in resource availability Single point of resource control Figure 3. Odyssey Client Architecture Wardens One per type Provide all type specific functionality Manage communication between client & server Offer menu of fidelity to application

6. 6 / 9 System Support for Mobile, Adaptive Applications Fidelity Measure of data quality The degree to which a data item used by a mobile client It is per type, not per application. Some different dimension is possible Related to adaptation policy Require knowledge of item or type’s structure Figure 1. Fidelity dimensions for images

7. 7 / 9 System Support for Mobile, Adaptive Applications Agility Agility The Limit on Adaptation Detecting change of resource availability Viceroy’s role By passive observation of network Trace network RPC latency & bulk transfer rate Estimate available bandwidth to server & notify application Application can adapt changed environment via adaptive decision loop

8. 8 / 9 System Support for Mobile, Adaptive Applications Stability Stability Improving the use experience If perceived difference between some fidelities is too large, User can’t tolerate of frequent, perceptual large changes Application must be skeptical of an increase in resource availability Viceroy’s role VS Application’s role Add information about expected variance of availability Application can decide their own stability

9. 9 / 9 System Support for Mobile, Adaptive Applications Conclusion Collaborative adaptation model OS : adaptation mechanism Application : adaptation policy Powerful model Consideration about Agility Stability

10. KAIS T Extras

11. 11 / 9 System Support for Mobile, Adaptive Applications Programming model A decision loop Adaptive applications are equipped to handle different fidelities proxy Figure 4. Adaptive Decision Loop