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Bluenet a New Scatternet Formation Scheme *

Bluenet a New Scatternet Formation Scheme *. Huseyin Ozgur Tan * Zifang Wang,Robert J.Thomas, Zygmunt Haas ECE Cornell Univ*. Outline. Introduction Bluenet Scheme Evaluation Methods Simulation Environment Simulation Results. Introduction. Performance issues for scatternet formation

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Bluenet a New Scatternet Formation Scheme *

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  1. Bluenet a New Scatternet Formation Scheme* Huseyin Ozgur Tan *Zifang Wang,Robert J.Thomas, Zygmunt Haas ECE Cornell Univ*

  2. Outline • Introduction • Bluenet Scheme • Evaluation Methods • Simulation Environment • Simulation Results

  3. Introduction • Performance issues for scatternet formation • Waste of capacity for bridge nodes • Resynchronization of radio from one piconet to another • Cost of some of network resources to maintain a scatternet • Master-Slave relation • Tradeoff • Decent level of Connectivity • Reserving enough network resources

  4. Introduction • Other scatternet formation schemes • At that time a few papers that address this problem • The most important one : Bluetree • In this paper proposed Bluenet and Bluetree algorithms are compared

  5. Bluetree • Two modes of formation • Blueroot Grown Bluetree • Distributed Bluetree • All resulting scatternets: spanning tree • Adv: spends the least of network resources • Disadv: • Reliability • If one parent node is lost, scatternet becomes disconnected • Efficiency • All traffic has to traverse the tree in upward and downward direction

  6. Bluenet Scheme • Background Information • Information exchange requires master slave relation • Try to construct the scatternet while forming master slave relations • Visibility graph • Network consisting of all the units and all the potential links • Scatternet is a small fraction of all the potential links • Scatternets are a subgraph of visibility graph • Intra piconet overhead • Polling and coordinating the slaves • Bridge overhead • Switching delay between different piconets • Standby -> Inquiry -> Page = master slave relation

  7. Bluenet Algorithm • Goal: efficient scatternet • Reasonable good connectivity but preserves network resources for communications. • The network resources should be spread as evenly as possible to prevent bottlenecks • 3 Rules • Rule 1: Avoid forming further piconets inside a piconet • Rule 2: For a bridge node, avoid setting up more than one connections to the same piconet • Rule 3: Inside a piconet the master tries to acquire some number of slaves

  8. Bluenet • Rule 1: • Since the traffic is well organized in a piconet • can be achieved if the master sends the list of its slaves to all its slaves • Rule 2: • To avoid excessive bridge overhead for the bridges • can be achieved if the units are capable of sending their piconet identity • Rule 3: • Size of the piconet effects final structure

  9. Bluenet • Phase I: Initial piconets are formed • Phase II: Separate Bluetooth node get connected • Phase III: Piconets get connected to form a scatternet

  10. Evaluation Methods • Average Shortest Path (ASP) • Average shortest path length among all 2-node pairs in a Bluetooth network • Only related with topology • ASP0 = minimal ASP obtained from visibility graph • ASPsct = actual ASP of the scatternet being evaluated • R = ASPsct /ASP0

  11. Evaluation Methods • Maximum Traffic Flows (MTF) • Important to learn about the information carrying capacity of network • MTF is based on maximum flow problem • The maximum amount of information that can be transmitted per unit time from source node s, to sink node t, without violating the link and node capacity limits. • Ford-Fulkerson Algorithm • If there is multiple sources and sinks problem of maximizing becomes maximum multi-commodity flows.

  12. Evaluation Methods • Algorithm for approximating MTF • A. calculate all maximum flows for all commodities by using Ford-Fulkerson method • B. Select the commodity pair with the largest maximum flow; then remove the commodity pair; and decrease the corresponding link capacities • C. repeat steps A&B until there is no commodity pair left. • The MFT is the sum of the largest maximum flows obtained from each run of b

  13. Simulation and Results • n, Bluetooth devices are randomly placed • Visibility graph is obtained • The scatternets are generated by Bluenet and Bluetree • Performance is evaluated

  14. Simulation Results • On ASP • 200 scatternet samples are generated • Mean ASP • Bluenet = 2.08 • Bluetree = 2.31

  15. Simulation Results • On MTF • 6 scatternets are formed for both schemes • 6000 randomly generated multi-commodities are used for calculation

  16. Conclusion • Advantages • Easily implementable on existing Bluetooth specs • Fast topology construction • No further information collection • Disadvantages • All devices are assumed to be turned on simultaneously • No mobility support • Static nodes

  17. Future Work • Must be compared with the new scatternet formation methods • Especially with Law & Siu’s method • Future work can be done on mobility support • dynamicity

  18. Thanks for patience Questions & Answers

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