1. KAIST Adaptive Triangular Deployment Algorithm for Unattended Mobile Sensor Networks Suho Yang (September 4, 2008) Ming Ma, Yuanyuan Yang IEEE Transactions On Computers 2007

2. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 Contents Introduction Assumption Ideal Node Layout for Maximum Coverage Two Triangular algorithms Basic Triangular Algorithm ATRI : Adaptive Triangular algorithm Performance Evaluation Conclusion 2

3. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 3 Wireless Sensor Networks Applications: military, environmental, health, home, commercial, … Strong points Small in size Low cost → can be densely deployed Weak points Low computational capacities and memory Short communication range Low power consumption requirement: the most important metric Other features Wireless communication Collaborative effort Fault tolerance Introduction

4. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 4 Deployment problem for WSN Problem 1: “Where to place sensors?” To maximize sensing coverage (using a certain number of sensors) =To minimize coverage gaps and overlaps → Propose the ideal node layout for maximum coverage Problem 2: “How to move sensors?” To minimize the total energy consumption to move sensors → Propose a distributed greedy heuristic algorithm Introduction

5. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 5 Assumptions All sensors are mobile sensors All sensors have the same capacities (=sensing range, energy, …) Omni-directional sensing No global information No location-awareness Each sensor only estimate the relative locations to neighbors Initially, all sensors are randomly deployed Assumption

6. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 Problem 1: “Where to place sensors?” - Ideal Node Layout for Maximum Coverage 6

7. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 7 The optimal node layout for the maximum no-gap coverage Equilateral triangulation Ideal Node Layout for Maximum Coverage

8. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 Proof The maximum value of can be obtained when In this case, the lengths of all three edges = 8 Ideal Node Layout for Maximum Coverage

9. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 Problem 2: “How to move sensors?” - Basic Triangular Deployment Algorithm 9

10. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 10 Main idea Each node divides the transmission circle into six sectors And adjusts the relative distance to its one-hop neighbors in each sector separately Basic Triangular Deployment Algorithm

11. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 11 Adjusting the distance between neighbors Notation Basic Triangular Deployment Algorithm where r = sensing range

12. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 12 Adjusting the distance between neighbors (cont.) Basic Triangular Deployment Algorithm

13. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 Adjusting the distance between neighbors (cont.) 13 Basic Triangular Deployment Algorithm

14. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 Adjusting the distance between neighbors (cont.) 14 Basic Triangular Deployment Algorithm

15. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 Algorithm 15 Basic Triangular Deployment Algorithm

16. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 16 Snapshots of the execution Basic Triangular Deployment Algorithm

17. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 17 Reducing node oscillation (1) Distance threshold strategy Constant threshold Variable threshold Basic Triangular Deployment Algorithm

18. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 18 Reducing node oscillation (2) Movement state diagram strategy Basic Triangular Deployment Algorithm

19. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 Problem 2: “How to move sensors?” - ATRI: Adaptive Triangular Deployment Algorithm 19

20. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 20 Additional consideration 1. Avoiding obstacles and boundaries 2. Non-uniform deployment ATRI: Adaptive Triangular Deployment Algorithm

21. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 21 1. Avoiding obstacles and boundaries Detect them with an ultrasonic obstacle-detecting module And abstract them as virtual nodes ATRI: Adaptive Triangular Deployment Algorithm

22. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 22 Snapshots of the execution for the environment with obstacles ATRI: Adaptive Triangular Deployment Algorithm

23. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 23 2. Non-uniform deployment The density of nodes can be adjusted adaptively to different requirements of tasks Strategy: set a shorter sensing range in important area ATRI: Adaptive Triangular Deployment Algorithm

24. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 24 Snapshots of the execution for non-uniform deployment ATRI: Adaptive Triangular Deployment Algorithm

25. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 Performance Evaluation Measurement of performance Deployment quality: total coverage area Moving energy consumption: moving distance Comparison with VEC in [G. Wang, G. Cao, and T. La Porta, “Movement-Assisted Sensor Deployment,” INFOCOM, 2004] 25

26. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 Performance Evaluation Total coverage area gets larger 26

27. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 Performance Evaluation Average moving distance gets smaller 27

28. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 28 The optimal node layout for maximum coverage Equilateral triangulation (the length of each side equals ) Basic Triangular Algorithm Divides the transmission circle into six sectors and adjust the relative distance between neighbors For reducing node oscillation Distance threshold strategy Movement state diagram strategy Adaptive Triangular algorithm Avoiding obstacles and boundaries Abstract them as virtual nodes Non-uniform deployment Set a shorter sensing range in important area Conclusion

29. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 29 The lack of mentions about Relation between communication range and sensing range Definition of some notations The meaning of some equations Termination condition No consideration about Communication overhead Deployment time Impact of threshold Synchronization and collision Discussion

30. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 Thank you 30

31. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 31 [1] I. Akyildiz, W. Su, Y. Sankarasubramaniam, and E. Cayirci, “Wireless Sensor Networks: A Survey,” Computer Networks, 2002. [2] G. Wang, G. Cao, and T. La Porta, “Movement-Assisted Sensor Deployment,” INFOCOM, 2004 References

32. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 32 What is Delaunay Triangulation? Appendix A: Delaunay Triangulation

33. Adaptive Triangular Deployment Algorithm for Unattended MSNs / 29 Minimum average moving distance Proof 33 Appendix B: Minimum average moving distance