1. A LOCALIZED SELF-HEALING ALGORITHM FOR NETWORKS OF MOVEABLE SENSOR NODES Mohamed Younis, Sookyoung Lee, Sheetal Gupta and Kevin Fisher Department of Computer Science and Electrical Engineering University of Maryland, Baltimore County IEEE Globecom 2008

2.  Introduction  Related work  DARA approach  RIM Approach  Simulation  NN approach  Conclusion

3.  A Wireless sensor and actor networks (WSAN) involves two types of nodes:  Sensors  Actors Command node Sensor node Actor Inter - actor communication Communication with the command node

4.  The failed actor serves as a cut-vertex node in the network Command node Sensor node Actor Inter - actor communication Communication with the command node

5. Actor Inter - actor communication A B C D E

6. Actor Inter - actor communication A B C D E

7. [11] A. Abbasi, K. Akkaya and M. Younis, “A Distributed Connectivity Restoration Algorithm in Wireless Sensor and Actor Networks,” in the Proceedings of the 32nd IEEE Conf. on Local Computer Networks (LCN’07), Dublin, Ireland, Oct. 2007.

8. 3 1 2 1 [11] A. Abbasi, K. Akkaya and M. Younis, “A Distributed Connectivity Restoration Algorithm in Wireless Sensor and Actor Networks,” in the Proceedings of the 32nd IEEE Conf. on Local Computer Networks (LCN’07), Dublin, Ireland, Oct. 2007.

9. [11] A. Abbasi, K. Akkaya and M. Younis, “A Distributed Connectivity Restoration Algorithm in Wireless Sensor and Actor Networks,” in the Proceedings of the 32nd IEEE Conf. on Local Computer Networks (LCN’07), Dublin, Ireland, Oct. 2007.

10.  The paper proposed only requires the knowledge of 1-hop neighbors approach.  Minimizes messaging overhead  Reduces the distance that individual nodes travel during the recovery

11.  Nodes know their position relative to their neighbors, not necessarily their exact coordinates.

12.  Each node broadcasts a HELLO message to introduce itself to its neighbors, then builds a list of directly reachable nodes.  Each table entry contains two parameters: {Node_ID, Relative position}

13.  Periodically send heartbeat messages to their neighbors to ensure that they are functional D E C A B F G H

14.  Move until they are a distance r/2 from the failed node D C A B F G H F r E

15.  This point is the closest intersection point of the two circles of radius r centered at B and C. D A B G H C E

16. C  Node D determines its new location based only on B’s position. D A B G H B r E

17. C D A B G H D r E  Node E determines its new location based only on D’s position.

18. Simulator????? Number of sensors300 mobile actor nodes Area size1000m × 1000m Initially placedrandom

20.  Every node is aware of its 2-hop neighbors D E C A B F G H D B F

24.  RIM is a distributed algorithm for Recovery through Inward Motion.  RIM minimizes messaging overhead and reduces the distance each individual node travels during the recovery.

26. A B G H F D C E F