dBBlue: low diameter and self-routing Bluetooth scatternet

This paper addresses the problem of scatternet formation for single-hop Bluetooth-based wireless ad hoc networks, with minimal communication overhead. We adopt the well-known structure de Bruijn graph to form the backbone of Bluetooth scatternet, hereafter called dBBlue, such that every master node has at most seven slaves, every slave node is in at most two piconets, and no node assumes both master and slave roles. Our structure dBBlue also enjoys a nice routing property: the diameter of the graph is O(logn) and we can find a path with at most O(logn) hops for every pair of nodes without any routing table, where n is the total number of nodes in the network. Moreover, the network congestion is at most O(logn/n), assuming that a unit of total traffic demand is equally distributed among all pair of nodes. We discuss in detail a vigorous method to locally update the structure dBBlue using at most O(logn) communications when a node joins or leaves the network. In most cases, the cost of updating the scatternet is actually O(1) since a node can join or leave without affecting the remaining scatternet. The number of affected nodes is always bounded from above by a constant when a node joins or leaves the network. The dBBlue scatternet can be constructed incrementally when the nodes join the network one by one. To facilitate the self-routing and easy updating, a scalable MAC assignment mechanism is designed to guarantee the packet delivery even during scatternet updating. In addition, the structure formed by our method can sustain the faults of 2 nodes and the network is still guaranteed to be connected. If a node detects a fault of some neighboring master node or bridge slave node, it can dynamically re-route the packets and the path traveled by the packet is still at most O(logn) hops. Previously no method can guarantee all these properties although some methods can achieve some of the properties.