Efficient flooding for wireless mesh networks

Abstract

Flooding in wireless mesh networks involves distributing some data from one node to rest of the nodes in the network. This dissertation proposes UFlood, a flooding protocol for wireless mesh networks that targets large file transfers, such as software updates, where achieving high throughput (minimizing the time to complete the flood to all nodes) and low airtime (lower the time each node spends in transmitting packets, and thus lower the impact on other wireless traffic) are both important. The central challenge in good flooding performance is the choice of senders for each transmission opportunity. At each time during a flood, some parts of the network will have received more data than others. The set of best sending nodes lies along the boundaries between these regions, and evolves with time in ways that are difficult to predict. UFlood's key new idea is a distributed heuristic to dynamically choose the senders likely to lead to all nodes receiving the flooded data in the least time. The mechanism takes into account which data nearby receivers already have as well as inter-node channel quality. The mechanism includes a novel bit-rate selection algorithm that trades off the speed of high bit-rates against the larger number of nodes likely to receive low bit-rates. Unusually, UFlood uses both random network coding to increase the usefulness of each transmission and detailed feedback about what data each receiver already has; the feedback is critical in deciding which node's coded transmission will have the most benefit to receivers. The required feedback is potentially voluminous, but UFlood includes novel techniques to reduce its cost. The dissertation concludes that careful choice of senders allows UFlood to achieve 150% higher throughput than MORE, a known high-throughput flooding protocol, using 65% less time transmitting. UFlood uses 54% lower airtime than MNP, an existing flooding protocol to minimize airtime, and achieves 300% higher throughput.