Fountain-Coded Multicast in Tactical Packet Radio Networks: Throughput Improvements Provided by Relay Nodes

We describe a method for employing relay nodes to enhance the performance of fountain-coded multicast for the delivery of a file from the source to multiple destinations in a tactical multi-hop networks of half-duplex packet radios. Our method uses a spanning tree, but it also permits relay nodes not on the tree to assist in the delivery of the file to the destinations. Each node exploits the broadcast nature of the wireless medium by attempting to overhear fountain-coded packets from senders other than the node's parents on the tree. No radio in the network is required to transmit multiple packets simultaneously or receive packets from multiple senders simultaneously. An adaptive modulation and channel coding protocol is used to mitigate the effects of time-varying propagation loss on the radio links of the network.