1. Preserving Area Coverage in Wireless Sensor Networks by using Surface Coverage Relay Dominating Sets Jean Carle, Antoine Gallais and David Simplot-Ryl IRCICA/LIFL, Univ. Lille 1, INRIA Futurs, France ISCC 2005 Speaker ： Shih-Yun, Hsu

2. Outline  Introduction  Assumption  Related works  Surface Coverage Relays - Connected Area Dominating Set (SCR-CADS) Algorithm  Relay Selection Phase  Decision Phase  Experimental Results  Conclusions

3. Introduction  Sensor nodes are low-cost, low-power, and multi-functional devices  Sensor nodes are deployed over hostile or remote environments to monitor a target area  Sensor nodes could monitor the whole environment  The network lifetime is important  Connected Area Dominating Set (CADS)

4. Introduction  Dominating sets  Dominating Set (DS)  Connected Dominating Set (CDS)  Area Dominating Set (ADS)  Connected Area Dominating Set (CADS)

5. Introduction A B C D E F G H

6. Dominating Set (DS) A B C D E F G H

7. Connected Dominating Set (CDS) A B C D E F G H

8. Area Dominating Set (ADS) A B C D E F G H

9. Connected Area Dominating Set (CADS) A B C D E F G H

10. Assumption  Sensing range is equal to communication range  Each node has a unique priority  Battery state  Identifier  Sensor nodes know their respective position  Positioning issue has already been addressed in other papers

11. Related works  A Coverage-Preserving Node Scheduling Scheme for Large Wireless Sensor Networks  WSNA workshop 2002  Propose a scheduling scheme which allows nodes to sleep or to remain active without compromising the network monitoring task  Blind point

12. Related works A B C D E F Blind Point

13. Related works D A B C

14. Surface Coverage Relays - Connected Area Dominating Set (SCR-CADS) Algorithm  Relay Selection Phase  Decision Phase

15. Relay Selection Phase  Computing connected dominated sets with multipoint relays  INRIA, Tech. Rep. 4597, Oct. 2002.  MultiPoint Relay (MPR)  Each two hop neighbor of the nodes has a neighbor in MPR set

16. Relay Selection Phase A C B F D E Sort(A)={NULL} Sort(A)={C} Sort(A)={C, E} Sort(A)={C, E, F} Sort(A)={C, E, F, D}

17. Relay Selection Phase  The node collects information of its neighbors  The node computes its own SCR set  The node broadcasts it to its neighbors

18. Decision Phase F A B C D E A B C E Sort(A)={B, C, E, D} F Sort(C)={…., F}

19. Decision Phase  The node collects relay sets and priorities of its neighbors  The node decides to be active if it has the highest priority or if its identifier is in the relay set of the neighbor with highest priority

20. Experimental Results  Experimental field ： 50 × 50  Sensing range = communication range = 10  Battery ： 100 units

21. Experimental Results

24. Conclusions  Surface Coverage Relays - Connected Area Dominating Set (SCR-CADS)  Without complex computation  Sensing range and communication are equal  Saves energy and prolongs the network lifetime  This provides energy savings and so prolongs the  network lifetime.

25. Thank You!!