Multicast scheduling for list requests

Abstract

Advances in wireless and optical communication, as well as in Internet multicast protocols, make broadcast and multicast methods an effective solution to disseminate data. In particular, repetitive server-initiated broadcast is an effective technique in wireless systems and is a scalable solution to relieve Internet hot spots. A critical issue for the performance of multicast data dissemination is the multicast schedule. Previous work focused on a model where each data item is requested by clients with a certain probability that is independent of past accesses. In this paper, we consider the more complex scenario where a client accesses pages in blocks (e.g., a HTML file and all its embedded images), thereby introducing dependencies in the pattern of accesses to data. We present a sequence of heuristics that exploit page access dependencies. We measured the resulting client-perceived delay on multiple Web server traces, and observed an average speed-up over previous methods ranging from 8% to 91%. We conclude that scheduling for multi-item requests is a critical factor for the performance of repetitive broadcast.

Broadcasting Images in Wireless Networks

“…Scheduling for multi-item retrieval has been considered in [3,9]. However, the access pattern in these works is different from the one considered in our work.…”

“…However, the access pattern in these works is different from the one considered in our work. The reason is that [3,9] concern broadcast items that are "linked" together (e.g., inline images within a web-page), thus consider programs where some items are accessed together with probability equal to one. In contrast, for image broadcasting, items are accessed together with probability determined by the required quality, which is user-defined.…”

“…In contrast, for image broadcasting, items are accessed together with probability determined by the required quality, which is user-defined. Moreover, in [3,9] there exist no order in the broadcast items, whereas in image broadcasting, items are ordered with respect to a transformation (e.g., discrete cosine). Programgeneration algorithms for retrieving numerical values in specified ranges, are examined by Tan et al [7].…”

On Minimum Circular Arrangement

“…Thus client access patterns often show dependencies between consecutive requests, so that the request for a data unit will make it more likely or less likely that certain data unit will be requested next. These access patterns must be taken into account while designing a good cyclic multicast schedule that has low client-perceived latency while accessing multi-item objects [19].…”

Improved Circular Layouts

“…This problem is reducible from the extensively studied NP-complete problem of Minimum Linear Arrangement [9]. Additional related circular arrangement problems and applications are mentioned in [6,14]. Another NP-hard problem is Circular Crossing Minimization [15], where the goal is to minimize the number of edge crossings in the layout.…”