GPS-Free Node Localization in Mobile Wireless Sensor Networks

1. GPS-Free Node Localizationin Mobile Wireless Sensor Networks H¨useyin Akcan1, Vassil Kriakov1,Herv´e Br¨onnimann1, Alex Delis2 1CIS Department Polytechnic University 2Dept. of Informatics & Telecom. University of Athens ACM MobiDE’06

2. Outline • Introductions • Localization Algorithm • Simulations • Conclusion

3. Introduction • Wireless sensor networks are composed of hundreds sensor nodes. • Sensor nodes • are capable of measuring various physical values. • are communicating with each other and organizing themselves to achieve mission. • find routing path by their relation between each other.

4. Introduction • Many applications require sensor network mobility in environments. • Some place there are not deployed sensor. • Ex. • The scene of a fire. • Emergency incident.

5. Introduction • Motivation • preserve network formation during directed mobility in mobile sensor networks. • Goals • provide directional neighbor localization in a network wide coordinate system. • work under fairly large motion and distance measurement errors. • unaffect by the speed of nodes. • work for any network size. • support a stable network in mobility problems.

6. Introduction • Explore accident location

7. Introduction

8. Introduction • Assumptions in this paper • Each mobile sensor node • has a compass pointing North • can measure the distance to their neighbors using (TOA). • allows each node to move a specific distance in a specific direction. • has no additional positioning equipment or infrastructure is required. • Actuator, compass and distance measurements are subject to errors caused by various real world disturbances.

9. Localization Algorithm • Core localization algorithm • Verification algorithm • Exceptional configurations

10. d1 d2 Localization Algorithm T=3 T=2 d1 T=1

11. d2 v1 V2 α2 α1 d1 Localization Algorithm • Core localization algorithm A B A B (X0 , Y0)

12. d2 v1 V2 α2 α1 d1 Localization Algorithm (X1 , Y1) A B A B (X0 , Y0)

13. d2 v1 V2 α2 α1 d1 Localization Algorithm (X1 , Y1) (X3 , Y3) A B B A (X0 , Y0) (X2 , Y2)

14. Localization Algorithm

15. Localization Algorithm

16. Localization Algorithm • CoreLocalization(n1, n2, v1,α1) • 1: d1 inter-distance(n1, n2) • 2: Move node n1 by v1 and α1 • 3: d2 inter-distance(n1, n2) • 4: Retrieve v2 and α2 from n2 • 5: Calculate positions of n2 using equations (4),(5) and (6)

17. d2 α2 Localization Algorithm (X2 , Y2) (X0 , Y0) d1 A B α1 V2 v1 B A (X3 , Y3) (X1 , Y1)

18. Localization Algorithm • Two possible position A A B B B A B A

19. Localization Algorithm • Verification (NeighborList NL) • 1: for each neighbor pair (m, n) in NL do • 2: if m and n are neighbors then • 3: dm,n measured inter-distance(m, n) • 4: for each position pair {mi, nj | i, j = 1, 2} do • 5: Compute Euclidean distance D between mi and nj • 6: if D = dm,n then • 7: mark mi and nj as exact positions

20. Localization Algorithm • Find dBC which are equal to d3. C C dBC dBC A B A B B A B A

21. Localization Algorithm • Exceptional configurations • If A=0 and B=0 then D=0 B B A B B A

22. Localization Algorithm • Exceptional configurations • If E2-DF<0 or G2-DH<0 • Node skip this round and make necessary adjustments.

23. Localization Algorithm T=2 T=1 d2 d3 d4 d1 d5

24. Simulations • Environment • Compare with absolute position algorithm • Sensor radio range 6 • 100 x 100 area • 100 run • Each round • random speed [0,5) • random angle [0,2π)

25. Simulations

26. Simulations • Random movement

27. Simulations • Directed movement

28. Simulations • Directed trajectory of nodes performing zig-zag movement.

29. Simulations • Absolute positioning algorithm

30. Simulations • Our localization algorithm

31. Conclusion • In this paper, they • are the first GPS-free localization algorithm work on mobile nodes. • propose a straightforward and robust algorithm that requires only a single round of node movement to localize all neighbor nodes.