Locally optimal Bluetooth Scatternet formation

The Bluetooth specification defines gateway nodes so that piconets communicate among each other in a seamless ad-hoc manner, forming scatternets. The specification also defines primitives for gateway nodes to divide their time between their piconets, but the actual mechanism and algorithms that this can be accomplished is left open. The time division in gateways effectively limits the network capacity and may introduce bottleneck points in the network. An inter-piconet scheduling (IPS) algorithm is required in order to efficiently coordinate the presence of gateways in the different piconets so that network capacity is maximized. This may be achieved by using rendezvous points –pre-negotiated slots that a piconet master agrees to poll the gateway, and the gateway agrees to have switched to that master’s frequency hopping sequence and accept the poll. We present an algorithm that sets up the rendezvous points between a gateway and its masters in a totally distributed fashion, while maximizing the throughput of the network. Whenever a node is decided to act as gateway between the already piconets it is already connected and the new piconet, a forwarding throughput function between all involving piconets is maximized. The function depends on locally known information and therefore the algorithm is naturally a distributed one. We present a rendezvous point assignment algorithm that maximizes the total network throughput and limits the creation of bottleneck gateway connections. The algorithm can be extended to support renegotiation of the RV-points and traffic requirements, if these are available at the IPS module.