Impact of topology on Bluetooth Scatternet

To utilize Bluetooth as a layer 2 multi‐hop subnet for global IP network, there are two missing protocols in current Bluetooth stack: network formation and routing. In this paper, we propose our network formation and routing protocols optimized for such Bluetooth subnset usage scenarios to fill this gap. In this paper, we first present some observations on performance degradations of Bluetooth PAN due to network topologies and topology change when radio independant protocols are implemented. And then we analyze the reason of performance degradation. Based on our analysis, we first propose a flexible scatternet formation algorithm under conference scenario for multi‐hop communication. By using proposed method, scatternet can be formed flexibly with star, mesh, or linked line based on several parameters like number of maximum piconets that a gateway Bluetooth device can participate, and whether loops are needed in the resulting scatternet to achieve better network performance. To utilize topology information in multi‐hop communication, we propose a Cross‐layer Optimized Routing for Bluetooth (CORB) CORB is a QoS‐extended AODV routing protocol with mainly two optimizations between networking layer and underlying Bluetooth MAC layer. The first optimization is to use a new load metric. (LM) in QoS routing protocol instead of number of hops in conventional best effort routing. LM is derived from estimation of nodes’ link bandwidth, which reflects the different roles of nodes in Bluetooth scatternet. This proposal helps routing protocol to bypass heavily loaded nodes, and find route with larger bandwidth. The second optimization is to adjust LM and some MAC layer parameters in response to the unstable network topology caused by movement and change of indoor radio condition. Finally, We present some simulation and experiment results based on implementation, which prove the effectiveness of our protocols.