Date Added: Jan 2010
Efficient, scalable and robust multicasting support from the MAC layer is needed for meeting the demands of multicast based applications over WiFi and mesh networks. However, the IEEE 802.11 protocol has no specific mechanism for multicasting. It implements multicasting using broadcasting at the base transmission rate. This paper identifies two fundamental reasons for performance limitations of this approach: Channel-state Indifference: irrespective of the current quality of the channel to the receivers, the transmission always uses the base transmission rate; Demand Ignorance: packets are transmitted by a node even if children in the multicast tree have received those packets by virtue of overhearing.