Multicast in 802.11 WLANs

Abstract

While the deployment of WiFi networks continue to grow at an explosive rate, the multicast multimedia delivery service on WiFi compliant devices is still in its early stage of development. The real culprit is the IEEE 802.11 MAC protocol, and in particular, the absence of feedback mechanism when multicast is used. Recently, a leader-based mechanism has been proposed to overcome this problem. In this paper, we measure the characteristics of the legacy multicast transmission mechanism and analyze its flaws. Then, we study the performance of the leader-based approach and compare its performance with the standard multicast service. The analysis is done on a large set of measurements made with our wireless testbed. Such measurements are an important complement to previous simulation studies and help in the design of the best mechanism to replace the faulty legacy multicast mechanism. Our study confirms that the leader-based mechanism outperforms the standard open-loop multicast mechanism while keeping fairness among other traffic.