1. A Distributed Localization Scheme for Wireless Sensor Networks with Improved Grid-Scan and Vector- Based Refinement Jang-Ping Sheu, Pei-Chun Chen, and Chih- Shun Hsu IEEE Transactions on Mobile Computing 2008

2. Outline Introduction Related Work Distributed Range-Free Localization Scheme Performance Evaluation Conclusions

3. Introduction Localization is a fundamental and essential issue for WSNs Many applications and communication protocols are based on location information Tracking Geographic-based routing Geocasting

4. Introduction Localization Algorithms Range-based TOA, TDOA, AOA, RSSI..etc. Range-free Centroid, APIT, DV-HOP, CPE..etc.

5. Introduction Range-based often need to be equipped with additional hardware are impractical solutions for WSNs Range-free Existing range-free schemes are either too costly (heavy traffic load), not accurate enough, or not scalable

6. Introduction To improve the previous works, this paper proposes a Distributed Range-Free Localization Scheme (DRLS) for static WSNs.

7. Related Work Centroid Algorithm

8. Related Work Convex Position Estimation (CPE) Algorithm

9. Distributed Range-Free Localization Scheme Beacon Exchange Improved Grid-Scan Algorithm Refinement The Impact of the Farther Anchor Refinement of the Estimated Location

10. Beacon Exchange Every anchor gathers the ID and location information of anchors within tow hops

11. Distributed Range-free Localization Scheme CPE DRLS

12. Improved Grid-Scan Algorithm 12332 23432 23432 12332 12111

14. Refinement The Impact of the Farther Anchor A1A1 A2A2 Anchor node Normal node Estimated location D invasion N’ N VF N’

15. Refinement Refinement of the Estimated Location D invasion A4max VF A4max

16. Refinement A1A1 A2A2 Anchor node Normal node N’ N Estimated location A3A3 A4A4 A5A5 L3L3 b c d e

17. Refinement A1A1 A2A2 Anchor node Normal node N’ N Estimated location A3A3 A4A4 A5A5 L3L3 c d D invasion A3max D invasion A3 VF A3max 3 3 3 3

18. Performance Evaluation Simulator : NS2 DOI (degree of irregularity) : 0.5 Area Size : 10r * 10r Number of nodes : 200

19. Performance Evaluation

22. Ratio of anchors = 40 percent

23. Performance Evaluation Anchor Ratio

24. Performance Evaluation Ratio of anchors = 33 percent

25. Performance Evaluation Number of sensor nodes = 25

26. Conclusions This paper proposes a fully distributed scheme range-free localization scheme for WSNs Simulation and experimental results show that the proposed scheme can achieve better accuracy than the other localization scheme

27. Thank You!