Cache Technology Research In The Mobile Environment

Recent advances in wireless data networking and portable computing devices haveengended a new pedigm of computing, called mobile computing. In a mobile computingsystem, users access information anytime anywhere with their handheld devices, even when theyare moving. Software is the most importan factor to prompting mobile computing. Mobilityconsthats break key assumptions associated with distributed computing. As a result, mostthaditional mechisms and algorithms have low performance in mobile environment.Caching is a classical technology to improve the perfotmane of data access. It has beensuccessfully applied to different fields of computing technlogy Caching will be even moreboortant in mobile systems because of resources ledtations of mobile devices and wirlessnetworks. This dissertation studies cache mangement in mobile computing environment fromthe perspective on the followin issues: autornated data hoarding and cache validation.The dissertaion first addreses data hoarding problem, which is raised by disconnectedoperahon. Disconnected operation is a challenging issue to all mobile systcms. Data hoardingalgorithm predicts data set of usees operation in the future. It is a major factor which affectscach hit rate when disconnected. We put forward the PDH algorithm which is an automated datahoarding algorithm based on probability graph. PDH algorithm effectively improves cache hitrate with light overhead. It is a practical algorithm, especially for handheld devices with smallcapacity of storage.To assure that applications never read dirty data, cache manager uses cache validationalgorithm to determine whether data in local cache is consistent with the primary copy on theserver. We propose a client/agendt/server based volume callback algorithm tO addrss two keyissues of callback-based algorithms: scalability and client disconnection. Agents improve systemscalability by mitigaing load on servers; volume callbacks accelerate revalidation process byincreasing granularity of vaidahon.We also extend the above client/agent/server based volume callback algorithm from thefollowing aspects. First, we propose a dynamic volume resizing mechanism for mobile Webbrowsing. Based on file's modify time, this dyndric mechanism, which is composed of splittingand combining procedurs, keePs each volum at proper size. Frequently changed files incline tobe moved tO the same volum. Shalation resultS shOw tha peffonnance of the above stronglyconsistent algOrithIn is close tO the wealdy consistent ATT algorith!n.8econd, we consider the twact of cliam mObility To suPPort seaInless roaIning of mobileclientS, we develoP a caCh statUS -- PrOtOcol, namd CSTP It allows caCh statUS of oneclient to be distributed on one or mere agents. Shadow agen is inhoduced to OPdrize messagerelay CSTP is distingUished by itS faSt registalon Process and server transParency The Wholevalidation algorithm, which suPPortS CSTP, is fOnnaly verified with the SPin model checker...