Efficient Multicast Scheme based on Hybrid ARQ and Busy Tone for Multimedia Traffic in Wireless LANs

Multicast in wireless LANs (Local Area Networks) is very useful for transmitting multimedia traffic from a sender to a group of receivers. The IEEE 802.11 WLAN MAC (Medium Access Control) layer does not support reliable multicast since, for multicast transmissions, it has no control packets such as the RTS, CTS, and ACK, which are used for unicast transmissions. Several protocols have been proposed to provide reliable multicast transmissions. However, they are not efficient for IEEE 802.11 WLANs due to the large number of packet transmissions and the excessive control overhead caused by the use of a large number of control packets in the error recovery process. In this paper, we propose a simple and effective scheme. The proposed scheme combines FEC (Forward Error Correction) and ARQ (Automatic Repeat reQuest) to reduce a large number of packet transmissions and to provide data reliability in the IEEE 802.11 WLANs multicast environment. It then uses busy tones to improve efficiency by reducing the excessive control overhead. Performance evaluation is conducted using both numerical analysis and simulation. The results show that the proposed scheme has good performance in terms of normalized throughput and average delay.