Power-Saving Mechanism for IEEE 802.11 Clients in a Multicast Multimedia Streaming Network

Wireless LAN multicast is a suitable mechanism for multimedia streaming because of its bandwidth efficiency. However, wireless multicast has several problems in terms of power efficiency. In this study, we analyze the power efficiency of multicast in IEEE 802.11 networks and show that multicast increases the power consumption of clients significantly irrespective of whether the clients join multicast groups or not. The main reason is that IP multicast packets are transferred as broadcast frames in IEEE 802.11 networks. To improve power efficiency, we propose a new multicast streaming mechanism. Our work is strongly motivated by Flexible Multicast Service (FMS), which is a new IEEE 802.11 standard. FMS permits access points (APs) to transmit multicast frames in more than one delivery traffic indication message (DTIM) interval, which allows clients to wake up at alternate DTIM intervals, rather than every DTIM. However, our analysis proved that FMS is not an optimal mechanism in terms of power efficiency. We propose a new mechanism that provides more power-efficient multicast multimedia streaming, without delay or throughput penalty. Our method focuses on how to reduce the number of unnecessary frames received by clients. The key idea is to stagger the transmission timing to let clients avoid receiving unnecessary frames. We evaluate the mechanism by comprehensive analysis and simulations. The results show that the mechanism achieves significant power savings in wireless LAN multicast networks.