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Abstract-In contrast to unicast routing, high-throughput reliable multicast routing in wireless mesh networks (WMNs) has received little attention. There are two primary challenges to supporting high-throughput, reliable multicast in WMNs. The first is no different from unicast: wireless links are inherently lossy due to varying channel conditions and interference. The second, known as the "crying baby" problem, is unique to multicast: the multicast source may have varying throughput to different multicast receivers, and hence trying to satisfy the reliability requirement for poorly connected receivers can potentially result in performance degradation for the rest of the receivers.In this paper, we propose Pacifier, a new high-throughput reliable multicast protocol for WMNs. Pacifier seamlessly integrates four building blocks, namely, tree-based opportunistic routing, intra-flow network coding, source rate limiting, and roundrobin batching, to support high-throughput, reliable multicast routing in WMNs, while at the same time effectively addresses the "crying baby" problem. Our evaluations show that Pacifier increases the average throughput over a practical, state-of-the-art reliable network coding-based protocol MORE by 171%, while improving the throughput of well-connected receivers by up to a factor of 20.

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In this paper, we develop a fast resource allocation algorithm that takes advantage of intra-session network coding. The algorithm maximizes the total utility of multiple unicast (or multicast) sessions subject to capacity constraints, where packets are coded within each session. Our solution is a primal solution that does not use duality or congestion prices. Thus, it does not require building up queues to achieve the optimal resource allocation. Hence, the queueing delay of the packets can be tightly controlled. The existing primal solution in the literature requires a separate graph-theoretic algorithm to find the min-cut of each session, whose complexity grows quadratically with the total number of nodes. In contrast, we provide a new coded-feedback approach whose complexity grows only linearly with the total number of nodes. More explicitly, by letting the ACK/feedback packets on the return paths also carry coding coefficients as does the forward coded traffic, key network information can be obtained more efficiently, which leads to a fast resource allocation scheme fully integrated with the network coding operation.