Distributed Hashing for Scalable Multicast in Wireless Ad Hoc Networks

摘要

Several multicast protocols for mobile ad hoc networks have been proposed that build multicast trees using location information available from GPS or localization algorithms and use geographic forwarding to forward packets down the multicast trees. These stateless multicast protocols carry encoded membership, location and tree information in each packet and are more efficient and robust than stateful protocols (ADMR, ODMRP) as they avoid the difficulty of maintaining distributed state in the presence of frequent topology changes. However, current stateless multicast protocols are not scalable to large groups because of the perpacket encoding overhead, and the centralized group membership and location management. We present the Hierarchical Rendezvous Point Multicast (HRPM) protocol which significantly improves the scalability of stateless multicast with respect to the group size. HRPM consists of two key design ideas: (1) hierarchical decomposition of a large group into a hierarchy of recursively organized manageable-sized subgroups, and (2) use of distributed geographic hashing to construct and maintain such a hierarchy at virtually no cost. Our detailed simulations demonstrates that HRPM achieves significantly enhanced scalability and performance due to hierarchical organization and distributed hashing.