1. Redeployment for Mobile Wireless Sensor Networks Weihong Fan, Hengyang Zhang and Xuanping Cai Yunhui Liu Yunhui LiuJoint Center of Intelligent Sensing and Systems National University of Defense Technology Department of Automation and Computer-Aided Engineering The Chinese University of Hong Kong Proceedings of the 2008 IEEE International Conference on Information and Automation IEEE ICIA 2008

2. Outline Introduction Problem Description DFS_LF Algorithm (Depth-First-Search_Leader-Follower) RHR_C Algorithm (Right-Hand-Rule_Centroid) Simulation Conclusion

3. Introduction The wireless sensor networks Application Environment surveillance Battlefield search/rescue Characteristic A large amount of sensor node A large range of area The sensors are deployed randomly

4. Introduction Random deployment Fragmentation phenomena Coverage hole problem Communication disc Communication or sensing disc

5. Related Work Solve the coverage problem Incremental sensor deployment ICPSAS 06 Movement assisted sensor deployment Grid coverage algorithm Voronoi diagram algorithm VFA and PFA

6. Network Modle Surveillance area A The total number of node : N Poisson distribution Poisson density : λ N/A → λ 0<λ<∞

7. Network Model All sensor nodes Mobile Homogeneous Location and orientation aware Rc : communication range Rs : sensing range Rc ≥2Rs

8. Network Model Communication area πR c 2 Sensing area : ||S|| Coverage max : max coverage ratio P(C) : coverage probability

9. DFS_LF Algorithm DFS algorithm + LF method DFS algorithm Select a virtual node as the collective object Flocking for Multi-Agent Dynamic Systems : Algorithms and Theory IEEE Transaction on automatic control, Vol. 51, No. 3, March 2006

10. DFS_LF Algorithm 2 1 4 5 3 6 8 7 9 Subnet A Subnet B collective object p : the position of collective object p i : the position of node i L L F1 F2 F3

11. DFS_LF Algorithm 8 7 9 collective object p : the position of collective object p i : the position of node i If d(p,p i )≤1/2R c need not move Else p i aims and moves to the object L 2 L F1 1 4 5 3 6 F2 F3 d(p i, p j ) ≤R c 1/2R c F1 F2 F3 F4

12. RHR_C Algorithm In the dense mobile sensor networks A large R c is likely to cause the congestion of communications traffic waste their limited energy Rc≥2Rs

13. RHR_C Algorithm If there is a communication hole, there must be a sensing coverage hole If the communication hole does not exit Discuss the relationship of communication range and sensing range Sensing coverage with no overlapping Sensing coverage with overlapping Rc≥2Rs +ε (ε>0)

14. RHR_C Algorithm detection coverage hole

15. Sensing coverage without overlapping

18. ε→0ε→0 X’(d ij )>0 rcrc X(d ij ) S 1

19. Sensing coverage with overlapping i j l k l‘ α B k RsRs

20. Sensing coverage with overlapping 22 2sinα

21. Sensing coverage with overlapping B α Y(α) sinα>0sinB-sinα>0 Y’(α)> 0 rcrc d jk d ki 1

22. Result From the two case The shorter communication distance between the sensor node and the higher sensing coverage ratio In the dense network r c ≥90.69% The coverage hole does not exits

23. RHR_C Algorithm Healing the communication hole RsRs

24. Simulation The interest area A : 80 x 60 m2 Rs = 2m DFS_LF algorithm Sensor nodes : 385 Rc = 5m Poisson density λ = 0.08 Coverage max =1.01 P(C) =0.57

27. Simulation RHR_C Algorithm Sensor nodes : 1000, 1200 R c = 4.1m Poisson density λ = 0.21 Coverage max =2.62 P(C) =0.93

30. Conclusion This paper propose two deployment algorithm for mobile sensor networks Fragmentation in sparse networks Coverage hole in dense networks Simulation result testify that the two algorithm are validity