1. Dynamic Proxy Tree-Based Data Dissemination Schemes for Wireless Sensor Networks Wensheng Zhang, Guohong Cao and Tom La Porta Department of Computer Science and Engineering The Pennsylvania State University IEEE International Conference on Mobile Ad-hoc and Sensor Systems (MASS) 2004 Speaker: Shin-Wei Ho

2. Outline Introduction System Model Distributed Tree Reconfiguration Schemes Performance Evaluations Conclusion

3. Introduction Applications of Sensor networks Battlefield surveillance Environmental control Security management Source and the sinks may frequently move.

4. Introduction

5. Tree-based multicasting scheme A sink may frequently fail to receive data Broken paths Tree should be frequently configured to reconnect sources and sinks.

6. Introduction Goal Dynamic proxy tree-based framework tree reconfiguration is conducted in an energy efficient way. minimize the data dissemination cost

7. System Model stationary sensor nodes each sensor node knows its own location some mobile hosts mobile target

8. System Model -- Dynamic Proxy Tree-Based Framework proxy does not change until its distance to the source (sink) exceeds a certain threshold

9. Distributed Tree Reconfiguration Schemes The problem of forming a minimum- cost proxy tree minimum Steiner tree NP-hard problem Need to collect information Shortest Path-Based (SP) Scheme Spanning Range-Based (SR) Scheme

10. Distributed Tree Reconfiguration Schemes -- Shortest Path-Based (SP) Scheme Basic Idea A new proxy should join the current proxy tree by attaching to the tree node that has the shortest distance to it.

11. Distributed Tree Reconfiguration Schemes -- Shortest Path-Based (SP) Scheme Proxy Join Step 1: Pre-searching join_req join_rep

12. Distributed Tree Reconfiguration Schemes -- Shortest Path-Based (SP) Scheme Proxy Join Step 2: Finding the closest node discover confirm

13. Distributed Tree Reconfiguration Schemes -- Shortest Path-Based (SP) Scheme Proxy Join Step 3: Node join Full Steiner tree Steiner Point

14. Distributed Tree Reconfiguration Schemes -- Shortest Path-Based (SP) Scheme leave_req Proxy leave

15. Distributed Tree Reconfiguration Schemes -- Shortest Path-Based (SP) Scheme Proxy leave

16. Distributed Tree Reconfiguration Schemes -- Shortest Path-Based (SP) Scheme Sink (Source) Movement Initiated Tree Reconfiguration a sink (source) moves and becomes far away from its proxy the current proxy should be changed to another node which is closer to the sink (source).

17. Distributed Tree Reconfiguration Schemes -- Shortest Path-Based (SP) Scheme Sink (Source) Movement Initiated Tree Reconfiguration Step 1: Establishing a temporary edge migrate_req

18. Distributed Tree Reconfiguration Schemes -- Shortest Path-Based (SP) Scheme Sink (Source) Movement Initiated Tree Reconfiguration Step 2: Finding the closest node

19. Distributed Tree Reconfiguration Schemes -- Shortest Path-Based (SP) Scheme Sink (Source) Movement Initiated Tree Reconfiguration Step 3: Joining the tree Steiner point Full Steiner tree

20. Distributed Tree Reconfiguration Schemes -- Shortest Path-Based (SP) Scheme Periodic Localized Tree Reconfiguration the subtrees that it leaves or joins are reconfigured the remaining part of the tree is untouched Each Steiner point node monitors the changes. Finds the optimal location for itself

21. Distributed Tree Reconfiguration Schemes -- Spanning Range-Based (SR) Scheme In the SP scheme, a new proxy needs to flood discover messages to find its position in the proxy tree. large overhead The Basic Idea Each subtree is assigned a certain spanning range

22. Distributed Tree Reconfiguration Schemes -- Spanning Range-Based (SR) Scheme The basic idea of the SR scheme

23. Distributed Tree Reconfiguration Schemes -- Spanning Range-Based (SR) Scheme The basic idea of the SR scheme

24. Distributed Tree Reconfiguration Schemes -- Spanning Range-Based (SR) Scheme Spanning Range Assignment

25. Distributed Tree Reconfiguration Schemes -- Spanning Range-Based (SR) Scheme

26. According to the spanning range assignment rule, each node on the tree decide the spanning range of its children send the range to them (piggybacked)

27. Distributed Tree Reconfiguration Schemes -- Spanning Range-Based (SR) Scheme Node Join Similar to the SP scheme, it selects a nearby sensor node Pn as its proxy and asks it to join the tree. Pn sends a join_req to the source proxy P

28. Distributed Tree Reconfiguration Schemes -- Spanning Range-Based (SR) Scheme P decides the location of Pn as follows: P calculates the spanning ranges of its children. Otherwise, P adds Pn as its child.

29. Distributed Tree Reconfiguration Schemes -- Spanning Range-Based (SR) Scheme

30. Sink Movement-Triggered Tree Reconfiguration If it is still in the range, Pi (the parent of Pn) follows the similar procedure of adding a new proxy. Otherwise, it forward add_req to its parent. pi pnPn ’

31. Distributed Tree Reconfiguration Schemes -- Spanning Range-Based (SR) Scheme Source Movement-Triggered Tree Reconfiguration P ’ P’P’ The change of root causes the other nodes in the tree to change their spanning ranges On receiving its new spanning range, each node Pn checks its children one by one

32. Performance Evaluations MATLAB 516, 2064 nodes 500×500, 1000×1000 square. 1 target 10 sinks NS2 802.11 MAC GPSR routing 516 nodes Communication range of 40m 500x500 square 1 target 10 sinks

33. Performance Evaluations -- Comparing the tree weights of different schemes (average velocity=2.5m/s, localized reconfiguration interval= 1s) MST SP SR

34. Performance Evaluations -- Comparing SR and SP

37. Performance Evaluation -- Impact of the localized reconfiguration mechanism ( SiMTR=Sink movement-initiated tree reconfiguration)

40. Performance Evaluations -- Impact of the SoMTP mechanism (average sink velocity=5.0m/s)

43. Conclusion In this paper, we addressed the problem of efficient dynamic multicasting in wireless sensor networks dynamic proxy tree-based framework Focused on the issue of efficiently reconfiguring the proxy tree The results showed that the SR scheme outperforms the SP scheme.

44. Question? Thank you.