1. My first aperosentation 9/6/2008 Marios Karagiannis

2. Localization

3. Problem: Nodes need to know their location

4. Localization Problem: Nodes need to know their location … so that applications like Target Tracking and Geographic Routing may actually work

5. Localization The “easy” way out: GPS

6. Localization The “easy” way out: GPS Well not quite, because GPS is:

7. Localization The “easy” way out: GPS Well not quite, because GPS is: -expensive

8. Localization The “easy” way out: GPS Well not quite, because GPS is: -expensive -big and heavy

9. Localization The “easy” way out: GPS Well not quite, because GPS is: -expensive -big and heavy -working only outdoors

10. Localization The “easy” way out: GPS Well not quite, because GPS is: -expensive -big and heavy -working only outdoors -working only on Earth

11. Localization The “easy” way out: GPS Well not quite, because GPS is: -expensive -big and heavy -working only outdoors -working only on Earth -controlled by the USA

12. Localization The “easy” way out: GPS Well not quite, because GPS is: -expensive -big and heavy -working only outdoors -working only on Earth -controlled by the USA -energy hungry

13. Localization The “easy” way out: GPS Well not quite, because GPS is: -expensive -big and heavy -working only outdoors -working only on Earth -controlled by the USA -energy hungry -not very accurate

14. Localization So what do we do?

15. Localization So what do we do? It depends. Is our node capable of detecting its distance from another node?

16. Localization So what do we do? It depends. Is our node capable of detecting its distance from another node? Range based approaches YES

17. Localization So what do we do? It depends. Is our node capable of detecting its distance from another node? Range based approaches Range free approaches YES NO

18. Localization Both approaches assume the existence of special nodes which already know their position

19. Localization Both approaches assume the existence of special nodes which already know their position These nodes are called anchors or beacons

20. Localization Each other node must use these special nodes to calculate an approximation of its own position

21. Localization Distance estimation may be calculated by using:

22. Localization Distance estimation may be calculated by using: Time difference of Arrival

23. Localization Distance estimation may be calculated by using: Time difference of Arrival By making the anchor send a radio and a sound signal at the same time, the node can calculate the distance by measuring the time difference between reception of the two signals

24. Localization Distance estimation may be calculated by using: Time difference of Arrival By making the anchor send a radio and a sound signal at the same time, the node can calculate the distance by measuring the time difference between receptions of the two signals This, of course, requires special equipment like tone generators and microphones

25. Localization Distance estimation may be calculated by using: Signal strength attenuation

26. Localization Distance estimation may be calculated by using: Signal strength attenuation By measuring the signal strength and compare it with the maximum strength possible, a node can estimate the distance the radio wave travelled

27. Localization Distance estimation may be calculated by using: Signal strength attenuation By measuring the signal strength and compare it with the maximum strength possible, a node can estimate the distance the radio wave travelled Of course this requires equipment capable of measuring the signal strength

28. Localization Trilateration

29. Localization Trilateration A B C n

30. Localization Trilateration A B C n n can be on any point of the circle’s perimeter

31. Localization Trilateration A B C n n can be either here or here

32. Localization Trilateration A B C n n know its position

33. Localization Trilateration A B C n When distance calculations are not precise, we have an approximation of the position

34. Localization Trilateration A B C n In this case, more than 3 anchors may help pinpoint the location D

35. Localization Range free estimation using hop count A B C n5 n10 n8 n3 n7 n4 n1 n2 n9 n6

36. Localization Range free estimation using hop count A B C n5 n10 n8 n3 n7 n4 n1 n2 n9 n6

37. Localization Range free estimation using hop count A B C n5 n10 n8 n3 n7 n4 n1 n2 n9 n6 N10 is at position (1,6,5)

38. Localization Range free estimation using hop count A B C n5 n10 n8 n3 n7 n4 n1 n2 n9 n6 because it is 1 hop from A, 6 hops from B and 5 hops from C

39. Localization Range free estimation using hop count A B C n5 n10 n8 n3 n7 n4 n1 n2 n9 n6 by knowing its communication radius, it has estimate its distances and so its position

40. Localization Range free estimation using hop count A B C n5 n10 n8 n3 n7 n4 n1 n2 n9 n6 So if it nodes that its radius is 1m, it may guess that it is 1 meter from A, 6 m from B and 5 m from C which is not that different from its real position

41. Localization Range free estimation using hop count A B C n5 n10 n8 n3 n7 n4 n1 n2 n9 n6 In a dense network, this method is more accurate

42. Localization Angle estimation n Supposed anchors A and C are equipped with lasers and n is equipped with a laser sensor A C

43. Localization Angle estimation Supposed anchors A and C are equipped with lasers and n is equipped with a laser sensor A C n

44. Localization Angle estimation n senses C’ laser at time t1 A C n

45. Localization Angle estimation n senses C’ laser at time t1 A C n

46. Localization Angle estimation n senses C’ laser at time t1 A C n

47. Localization Angle estimation n senses C’ laser at time t1 A C n n senses A’ laser at time t2

48. Localization Angle estimation n senses C’ laser at time t1 A C n n senses A’ laser at time t2

49. Localization Angle estimation n senses C’ laser at time t1 A C n n senses A’ laser at time t2

50. Localization Angle estimation n senses C’ laser at time t1 A C n n senses A’ laser at time t2

51. Localization Angle estimation n senses C’ laser at time t1 A C n n senses A’ laser at time t2 n senses A’ laser again at time t3

52. Localization Angle estimation n senses C’ laser at time t1 A C n n senses A’ laser at time t2 n senses A’ laser again at time t3

53. Localization Angle estimation n senses C’ laser at time t1 A C n n senses A’ laser at time t2 n senses A’ laser again at time t3

54. Localization Angle estimation n senses C’ laser at time t1 A C n n senses A’ laser at time t2 n senses A’ laser again at time t3 n senses C’ laser again at time t4

55. Localization Angle estimation By knowing: A’s and C’ laser rotation rate A’s and C’ laser maximum and minimum angles n can calculate the angles to A and C based on t1,t2,t3 and t4 A C n

56. Localization Angle estimation It takes just 2 anchors for this technique but result is a scale-prone model of the network A C n

57. Localization When a node becomes localized it then transforms to a new anchor

58. Localization When a node becomes localized it then transforms to a new anchor Because it is an anchor, it will broadcast its own position in order to help other nodes localize as well

59. Localization If all nodes which becomes anchors broadcast greedily, we will localize the whole network

60. Localization If all nodes which becomes anchors broadcast greedily, we will localize the whole network But should they?

61. Localization In this case we will have lots of collisions!

62. Localization In this case we will have lots of collisions! Unless we introduce delays randomly or semi-randomly

63. Localization

70. The network is localized

71. Localization Our goal is to introduce a mechanism that will reduce the number of broadcasts in order to:

72. Localization Our goal is to introduce a mechanism that will reduce the number of broadcasts in order to: Save energy

73. Localization Our goal is to introduce a mechanism that will reduce the number of broadcasts in order to: Save energy Avoid collisions

74. Localization Our goal is to introduce a mechanism that will reduce the number of broadcasts in order to: Save energy Avoid collisions Localize the network in a shorter time

75. Localization In order to do that, a node that has been recently localized must decide to broadcast its position

76. Localization In order to do that, a node that has been recently localized must decide to broadcast its position or not

77. As described in Localization algorithm for wireless ad-hoc sensor networks with traffic overhead minimization by emission inhibition Pierre Leone, Luminita Moraru, Olivier Powell, Jose Rolim

78. Localization B A C

79. B A C 3 covered

80. Localization B A C 3 covered 2 covered

81. Localization B A C 3 covered 2 covered 1 covered

82. Localization B A C 3 covered 2 covered 1 covered Naturally 3 covered will be localized

83. Localization B A C 3 covered 2 covered 1 covered If they all broadcast at different times many nodes will receive more than 3 anchors

84. Localization B A C 3 covered 2 covered 1 covered This is unnecessary!

85. Localization B A C 3 covered 2 covered 1 covered We only need to make sure that nodes that need one more to localize (2 covered)

86. Localization B A C 3 covered 2 covered 1 covered will get one more anchor!

87. Localization B A C 3 covered 2 covered 1 covered So, we give a timer to each newly localized node depending on its distance from

88. Localization B A C 3 covered 2 covered 1 covered a critical point!

89. Localization B A C 3 covered 2 covered 1 covered So how do we calculate a critical point?

90. Localization B A C We find the intersection points for each pair of circles

91. Localization B A C A critical point can be here or here for the circles of A and B

92. Localization B A C Which one do we choose?

93. Localization B A C We choose the one that is not Inside the circle of C

94. Localization B A C We choose the one that is not Inside the circle of C

95. Localization B A C

96. B A C 3 covered 2 covered 1 covered By repeating this procedure for all 3 pairs we find the 3 critical points

97. Localization B A C 3 covered 2 covered 1 covered

98. Localization B A C 3 covered 2 covered 1 covered Nodes closer to the critical points will broadcast first

99. Localization B A C 3 covered 2 covered 1 covered Nodes closer to the critical points will broadcast first

100. Localization B A C 3 covered 2 covered 1 covered This happens by setting a timer for each node in the 3 covered area

101. Localization B A C 3 covered 2 covered 1 covered The timer is proportional to the distance d to its closest critical point or to d 2

102. Localization B A C 3 covered 2 covered 1 covered Other nodes will wait for their turn, but will not broadcast at all if they hear another node broadcasting which is closer to their critical point

103. Localization B A C 2 covered 1 covered Other nodes will wait for their turn, but will not broadcast at all if they hear another node broadcasting which is closer to their critical point

104. Localization B A C 2 covered 1 covered In this case we maximize nodes that are in 2 covered areas

105. Localization B A C 2 covered 1 covered In this case we maximize nodes that are in 2 covered areas

106. Localization Experiments have shown that this technique achieves the goals set before!

107. Thank you