1. 1 dBBlue:Low Diameter and Self-routing Bluetooth Scatternet Wen-Zhan Song, Xiang-Yang Li, Yu Wang and Weizhao Wang Department of Computer Science Illinois Institute of Technology ACM Dialm-POMC 2003, San Diego, CA

2. Wen-Zhan Song Illinois Institute of Technology 2 Outline Problem Statement Previous Works Our Contributions Static Scatternet Construction Localized Scatternet Updating Labeling Rules and MAC Assignment Self-Routing in Scatternet Conclusion and Future Work

3. Wen-Zhan Song Illinois Institute of Technology 3 Scatternet Formation Problem (a) Piconet(b) Scatternet Master Bridge Slave

4. Wen-Zhan Song Illinois Institute of Technology 4 Preferred Properties Preferred Properties on Scatternet Topology: Bounded node degree Single role for each node Low diameter Easy to update Enable efficient routing dBBlue protocol can achieve more beyond these ……

5. Wen-Zhan Song Illinois Institute of Technology 5 dBBlue Scatternet Property Bounded Node Degree – Master: 7, Pure Slave: 1, Bridge Slave: 2 Single Role per Node – Master or Slave, never switch role during communication Low Diameter – 2m+2 where Self-routing – for any given source-target pairs, a path with at most 2m+2 hops can be found without routing table Locally Update – the communication cost of updating is O(1) in most cases, O(log n) in worst case Low Congestion – about O(log n/n) communication load per node assuming a unit of total traffic demand among all pairs Fault-tolerance – 2-Connectivity in backbone Easy for scatternet schedule – because of our MAC assignment

6. Wen-Zhan Song Illinois Institute of Technology 6 Previous Works Tree Structure: Zaruba, Basagni and Chlamtac – number of roles is smaller than 3, need routing table Tan, Miu, Guttag and Balakrishnan – self-routing derivated from binary tree, update is not localized Ring Topology Sun, Chang and Lai – 2-connectivity, no routing table, O(n) diameter, number of piconets Projective Scatternet Barriere, Fraigniaud, Narajanan and Opatrny – degree bounded, low diameter,self-routing, update cost O(log 4 n log 4 log n)

7. 7 dBBlue Scatternet Construction

8. Wen-Zhan Song Illinois Institute of Technology 8 de Bruijn Graph 001011 100110 000101010 111 de Bruijn graph B(d,k) is a directed graph consists of d k nodes. Each node has a unique length-k label x 1 x 2 …x k and has d directed edges to nodes set {x 2 …x k y}, where

9. Wen-Zhan Song Illinois Institute of Technology 9 de Bruijn Graph 001011 100110 000101010 111 Routing from x 1 x 2 …x k to y 1 y 2 …y k follows: x 1 x 2 …x k  x 2 …x k y 1  x 3 …x k y 1 y 2  …  y 1 y 2 …y k Shortcut path can be followed by always looking for the longest match between the suffix of intermediate node and the prefix of target y 1 y 2 …y k s t X X X 010101 001011

10. Wen-Zhan Song Illinois Institute of Technology 10 Topology Choice 1 001011 100110 000101010 111

11. Wen-Zhan Song Illinois Institute of Technology 11 Topology Choice 2 001011 100110 000101010 111

12. Wen-Zhan Song Illinois Institute of Technology 12 Topology Choice 3 - dBBlue A dBBlue scatternet containing 48 nodes with B(2,3) as the backbone 001011 100110 000101010 111

13. Wen-Zhan Song Illinois Institute of Technology 13 Static Scatternet Construction Given n nodes, a leader initiates the construction by selecting master nodes to form the backbone. Each master node distributely invites some slave nodes to form the final topology – dBBlue scatternet.

14. Wen-Zhan Song Illinois Institute of Technology 14 Illustration of dBBlue in Tree level m …… i-1ii+1 token

15. 15 Localized Scatternet Updating

16. Wen-Zhan Song Illinois Institute of Technology 16 Pseudo-balanced de Bruijn Graph The figure illustrates the correspondence between full binary tree and generalized de Bruijn graph. Pseudo-balanced de Bruijn graph: label length difference at most 1

17. Wen-Zhan Song Illinois Institute of Technology 17 Node Joining – Case 1 level m …… i-1i i+1 level m+1 token

18. Wen-Zhan Song Illinois Institute of Technology 18 Node Joining – Case 1 level m …… i-1i i+1 level m+1 token

19. Wen-Zhan Song Illinois Institute of Technology 19 Node Joining – Case 2 level m …… i-1i i+1 level m+1 token Piconet split

20. Wen-Zhan Song Illinois Institute of Technology 20 Piconet Split Our MAC assignment in piconet can guarantee the message delivery even during piconet split. Details refer to paper.

21. Wen-Zhan Song Illinois Institute of Technology 21 Node Leaving – Case 1 Token node need find a free slave to replace the leaving node. level m …… i-1i i+1 level m+1 token leaving

22. Wen-Zhan Song Illinois Institute of Technology 22 Node Leaving – Case 1 Token node need find a free slave to replace the leaving node. level m …… i-1i i+1 level m+1 token

23. Wen-Zhan Song Illinois Institute of Technology 23 Node Leaving – Case 2 Token node need find a free slave to replace the leaving node. level m …… i-1i i+1 level m+1 token Piconet merge leaving

24. Wen-Zhan Song Illinois Institute of Technology 24 Piconet Merge Our MAC assignment in piconet can guarantee the message delivery even during piconet split. Details refer to paper.

25. Wen-Zhan Song Illinois Institute of Technology 25 Scatternet Transform Balanced Expanding Shrinking _ ++ _

26. 26 Labeling Rules and MAC Assignment

27. Wen-Zhan Song Illinois Institute of Technology 27 Define Node Labels Node label = (PiconetID, MAC) PiconetID – m-bits de Bruijn label of master node, i.e, x 1 x 2 …x m MAC – 3-bits, 000 ~ 111, corresponding to time slot for intra-piconet communication. Notice that bridge node could have two different PiconetIDs and MACs, its label is only consistent with the in-master.

28. Wen-Zhan Song Illinois Institute of Technology 28 A Piconet in dBBlue Scatternet In the figure, slave node v i has MAC i (3-bits, 001~111) 000 – master; 100 – pure slave 011, 111 – two in-bridge slaves 010,101,001,110 – out-bridge slaves and pure slaves

29. Wen-Zhan Song Illinois Institute of Technology 29 Case 1: Two out-neighbors

30. Wen-Zhan Song Illinois Institute of Technology 30 Case 2: One out-neighbor

31. Wen-Zhan Song Illinois Institute of Technology 31 Case 3: Three out-neighbors

32. Wen-Zhan Song Illinois Institute of Technology 32 Case 4: Four out-neighbors

33. Wen-Zhan Song Illinois Institute of Technology 33 Summary of MAC Assignment Current Piconet In-NeighborOut- Neighbor yx 1 …x r x 2 …x s x 2 …x s y 1 x 2 …x s y 1 y 2 x 1 …x s y11010 _y1y1y1_y1y1y1 _y1y2y2_y1y2y2 Advantages of the MAC assignment Facilitate the routing Communication resilience during topology update Easy for inter-piconet scheduling

34. 34 Routing in Scatternet

35. Wen-Zhan Song Illinois Institute of Technology 35 Master to Master 001011 100110 000101010 111 S t MAC 101 MAC 010MAC 101 MAC 010

36. Wen-Zhan Song Illinois Institute of Technology 36 Conclusion and Future Work Efficient Scatternet Construction Formation and Routing without geometric information Low diameter, self routing, load balance Easy inter-piconet scheduling Implicitly facilitate future P2P applications How to extend to a multi-hop Bluetooth scatternet?

37. 37 Homepage: http://www.iit.edu/~songwenhttp://www.iit.edu/~songwen Email: songwen@iit.edu