Bridging the Gap between Response Time and Energy-Efficiency in Broadcast Schedule Design

Broadcast program generation for Webcasting

“…Five approaches considered so far this partitioning problem [23][24][25][26][27]--we defer the detailed presentation of these methods until Section 2.2, where we derive some bound for their time complexity. Nevertheless, none of these approaches can produce programs able to address both requirements of the Webcasting environment (or any other large scale broadcasting environment e.g., [12]), namely (a) skewed access pattern and (b) very large number of items transmitted.…”

“…Consequently, it is very fast in creating the respective program, but it is vulnerable to skewed access probabilities. The works in [24][25][26][27] are more sophisticated, in that they try to deal with non-uniformity in access probabilities and thus to produce better programs, but require very large processing time when the number of items to be transmitted is more than a thousand, thus they do not exhibit good scalability in terms of the data set size.…”

“…The work in [26] remedies a disadvantage of the previous one which appears when the number of disks is not a power of 2. Finally, the work in [27] is based on [25], but its nature is closer to a dynamic programming approach rather than to a greedy one.…”

“…In the top-down [25][26][27] we start from a large partition, possibly including all the items, and gradually split it into smaller pieces. In the bottom-up [24] we start with many small partitions which gradually grow, whereas the one-scan approach makes a single scan over P assigning items to disks based on some criterion.…”

“…Although the problem of broadcast disks is twofold, that is, it consists of the determination of the disk frequencies and the contents of each disk, the latter one is much harder, as the extensive research work on it reveals. Thus, the fundamental decision in any Webcasting system implementing the broadcast disks paradigm is the partitioning of items into groups, each one of the groups corresponding to a broadcast disk [23][24][25][26][27]. The present work deals with the issue of creating hierarchical broadcast programs for Webcasting and the issues of caching/prefetching and index broadcast are orthogonal to our work.…”