A new hybrid broadcast scheduling algorithm for asymmetric communication systems

Abstract

It is believed that broadcast is an efficient way to transmit data in an asymmetric communication system. Most of the previous work focused on either pull-based or push-based scheduling. However, for systems with a very large number of data items, none of these schemes is efficient individually. We propose a novel hybrid scheduling algorithm which uses both pull- and push-based schemes. In our approach, data items are divided, by a suitable cut-off point, into two disjoint sets: one consisting of more-popular items and the other of less-popular items. The items in the former set are broadcast by a push-based schedule, while those in the latter set by a pull-based schedule. A cut-off point is said to be optimal when it minimizes the expected access time in the system. The optimal cut-off point is derived analytically and validated by simulation experiments. Results show that the proposed hybrid push- and pull-based scheduling performs always better than a pure push-based scheduling and improves on the expected access time of an existing hybrid scheduling scheme.