DIMACS TR: 95-11

Airdisks and AirRAID: Modeling and scheduling periodic wireless da ta broadcast

Authors: Ravi Jain, John Werth


We introduce a simple model, called the airdisk, for modeling the access of data transmitted periodically over wireless media as being analogous to the access of data from a standard magnetic disk. We consider several issues related to airdisks, such as their mean rotational latency under certain assumptions. The problem of scheduling the order in which data items are broadcast is analogous to that of determining how data should be laid out on the disk. Two problems of laying out data so as to minimize read time, given information about which data items are of most interest to the clients, are defined; both are shown to be NP-complete. We discuss ways in which the information about which items are of interest to clients can be obtained. Finally we consider how to increase the performance and storage capacity of airdisks, using the magnetic disk analogy as a guide. We suggest using multiple-track airdisks or borrowing the idea of Redundant Arrays of Inexpensive Disks (RAID) which is used for magnetic disks; for the wireless data broadcast environment we call the latter approach airRAID.

Paper available at: ftp://dimacs.rutgers.edu/pub/dimacs/TechnicalReports/TechReports/1995/95-11.ps.gz
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