Date Added: Sep 2009
In this paper, authors describe oCast, an energy-optimal multicast routing protocol for wireless sensor networks. The general minimum-energy multicast problem is NP-hard. Intermittent connectivity that results from duty-cycling further complicates the problem. Nevertheless, authors present both a centralized and distributed algorithm that are provably optimal when the number of destinations is small. This model is motivated by scenarios where sensors report to a small number of base stations or where data needs to be replicated on a small number of other nodes. Authors further propose an extended version of oCast, called Delay Bounded oCast (DB-oCast), which can discover optimal multicast trees under a predefined delay bound. Finally, authors demonstrate the advantages of the schemes through both theoretical analysis and simulations.