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End-to-end Adaptive Multimedia over Bluetooth Scatternets


Bluetooth Scatternet enabled technology today exists only in the standards not the actual chips. Even though the standard defines the primitives to support scatterneting, the architectural options are left open to research. In this paper we use a number of proposed solutions and implemented models to explore application and transport behavior in Bluetooth scatternets. We specifically look at multimedia end-to-end adaptive applications, since this type is expected to be popular in scatternets in personal area network communication as well as other commercial and military applications. We limit our study to a ‘trial-anderror’ adaptation mechanism, which is based on the simple RTP suggested loss rate observation. Furthermore, since mobility support for Scatternets is minimal today, we only regard cases where mobility does not effectively change the network structure. We take our study one step further by including a strictly, as much as possible, MAC layer comparison between the structured Bluetooth MAC and the totally asynchronous 802.11/DCF MAC, both suggested for infrastructureless networks. Our study suggests that in Bluetooth even though gateways effectively limit the network capacity at a fraction of the link data rate, closed loop end-to-end adaptation can be effective in controlling congestion and improving user perceived QoS. This is attributed to the very controlled master centric polling MAC layer in combination with the time invariant inter-piconet scheduling architecture we use. On the other hand, the 802.11 limited to Bluetooth characteristics for the shake of our comparison, shows significantly less effective throughput in all cases, and a more inefficient response to adaptive traffic. We studied the traffic behavior of such applications in scatternets of up to 16 piconets and 64 nodes. We conclude that simple end-to-end adaptive closed loop congestion control can be very effective in Bluetooth piconets and scatternets, and more effective than in more asynchronous unstructured MAC layers when mobility is low. The choice between a structured and an asynchronous MAC layer should be made based on how well the more efficient structured MAC can support mobility.

Paper: PDF file of paper

Information & Date

EuroComm, Brussels, Belgium, December. 2002


Manthos Kazantzidis
Andrea Zanella
Mario Gerla