Reliable multicast over wireless ad-hoc network

IEEE 802.11 is the de facto standard for wireless communications. According to the 802.1 1 medium access control protocol, multicast frames are transmitted over ad hoc networks without virtual channel reservation. Hence, multicast communications in ad hoc networks suffer from the hidden terminal problem, and may have low delivery ratio. Feedback implosion is another issue that need to be addressed. If each multicast group member sends feedback messages to the sender directly, the sender will be congested/overloaded. In this research, a tree-based reliable multicast communication protocol is proposed. Firstly, the virtual channel reservation technique for unicast communication is extended to multicast communications such that the packet loss probability can be reduced significantly. Secondly, a tree-based packet recovery protocol is developed. Feedbacks from the multicast group members are consolidated at the branch points of the multicast tree, and the workload of the packet recovery process can be distributed among the multicast group members. The performance of the proposed reliable multicast protocol is studied via simulation. It was found that the tree-based method performs better than gossip-based methods when node mobility is not high.

Author: Lau, Kwan Shek

Source: City University of Hong Kong

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