A new design of the IEEE 802.11 MAC layer to enhance the scalability of the DMS service

The IEEE 802.11v defines the Directed Multicast Service (DMS) in order to enhance the reliability of the multicast transport. This service converts multicast traffic into several unicast streams. Therefore DMS can be used to serve a limited number of receivers. In this paper, we show that using DMS, losses caused by queue rejections may exceed the packet loss rate of the legacy multicast. To resolve the limited scalability of DMS, we define a new scalable version called S-DMS. This version is appropriate for layered streams like H264/SVC and is able to avoid queue overflows. S-DMS delivers the base layer of a video traffic using DMS and transmits the enhancement layer using either DMS or the legacy multicast, depending on the available bandwidth. We show that S-DMS is able to increase considerably the number of admitted multicast members.