Scheduling and caching strategies for broadcasting correlated data
Proceedings of the 2001 ACM symposium on Applied computing
Windows scheduling problems for broadcast systems
SODA '02 Proceedings of the thirteenth annual ACM-SIAM symposium on Discrete algorithms
Scheduling and caching strategies for correlated data in push-based information systems
ACM SIGAPP Applied Computing Review
Pushing dependent data in clients-providers-servers systems
Wireless Networks
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RRecently there has been considerable interest in delivering information to distributed mobile clients via wireless broadcast. Information transmitted periodically over wireless media can be regarded as a virtual disk, which we call an airdisk, analogous to a standard magnetic disk. Airdisks offer an efficient mechanism for delivering personalized information services from a fixed server to large numbers of geographically distributed mobile clients, by broadcasting data and allowing clients to filter out the items of interest to them. Mobile clients are typically portable devices or Personal Digital Assistants which have restricted resources, and operate using limited battery power. We study the problem of scheduling the order in which data items are broadcast so as to minimize the access time of the clients. We observe that the problem is analogous to that of determining how data should be laid out on the disk, and show that the problem is in general NP-complete. We then focus on the data layout problem in the situation where the server inserts an index at the start of each broadcast period. We develop a branch-and-bound procedure for solving the problem optimally, and then develop a fast, simple heuristic. We present the results of simulation experiments to evaluate these procedures. As expected, the branch-and-branch procedure produces optimal solutions substantially faster than a naive enumeration algorithm. However, the heuristic is found to run substantially faster than the branch-and-bound procedure, and yet produces schedules that are only slightly longer. We end with a brief discussion of further experimental work in progress and conclude with a summary.