Formation, routing, and maintenance protocols for the BlueRing scatternet of Bluetooths

The basic networking unit in Bluetooth is piconet, and a larger-area Bluetooth network can be formed by multiple piconets, called scatternet. However, the structure of scatternets is not defined in the Bluetooth specification and remains as an open issue at the designers´ choice. It is desirable to have simple yet efficient scatternet topologies with well supports of routing protocols, considering that Bluetooths are to be used for personal-area networks with design goals of simplicity and compactness. In the literature, although many routing protocols have been proposed for mobile ad hoc networks, directly applying them poses a problem due to Bluetooth´s special baseband and MAC-layer features. In this work, we propose an attractive scatternet topology called BlueRing which connects piconets as a ring interleaved by bridges between piconets, and address its formation, routing, and topology maintenance protocols. The BlueRing architecture enjoys the following nice features. First, routing on BlueRing is stateless in the sense that no routing information needs to be kept by any host once the ring is formed. This would be favourable for environments such as Smart Homes where computing capability is limited. Second, the architecture is scalable to median-size scatternets easily (e.g., around 50∼70 Bluetooth units). In comparison, most star- or tree-like scatternet topologies can easily form a communication bottleneck at the root of the tree as the network enlarges. Third, maintaining a BlueRing is an easy job even as some Bluetooth units join or leave the network. To tolerate single-point failure, we propose a protocol-level remedy mechanism. To tolerate multi-point failure, we propose a recovery mechanism to reconnect the BlueRing. Graceful failure is tolerable as long as no two or more critical points fail at the same time. As far as we know, the fault-tolerant issue has not been properly addressed by existing scatternet protocols yet. In addition, we also evaluate the ideal network throughput at different BlueRing sizes and configurations by mathematical analysis. Simulations results are presented, which demonstrate that BlueRing outperforms other scatternet structures with higher network throughput and moderate packet delay.