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차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
multimediacomputing laboratory
MAL(Mobile-Assisted Localization) in Wireless Sensor Networks
Choi Chang-hee MMC lab.
Proceedings of IEEE INFOCOM, March 2005. Nissanka B. Priyantha(MIT)
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
multimediacomputing laboratory
Index
1. Introduction2. Rigidity Theory3. MAL – Distance Measurement4. MAL – Movement Strategy5. Performance Evaluation6. Conclusion
2
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
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Introduction
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
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IntroductionWhat is the Localization Problem?
• Determine an assignment of coordinates
Node 1
Node 2 Node 3
Input
Node 1
Node 2 Node 3
(0,0) (4,0)
(0,3)
Output
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
multimediacomputing laboratory5
IntroductionSteps of Localization
DistanceMeasurement Localization
Using MAL
Using MAL & AFL( Another paper )
In this paper,
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
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Introduction
• Manually ( ex : Ruler, laser, etc… )• Ultrasonic on sensor node
Previous Methods – Distance Measurement
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
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Introduction
• Physical obstacles ( in especially indoors )• Non-omni-directional hardware• Few distance information
Problem with Previous Methods in Practice
Response curves of the sensorSU-D2000-M30N-C1-POS
Very many obstacles in my life Few data
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
multimediacomputing laboratory8
Introduction
• Use mobility to estimate location!!– Roving human, robot, etc…
Proposed Method
Node 2 Node 3Node 1
Node 4
Ob sta
cle
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
multimediacomputing laboratory9
Rigidity Theory
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
multimediacomputing laboratory10
Rigidity Theory
• Suppose C is a collection of mathematical objects , C is rigid if every c Є C is uniquely determined by less information c about than one would expect.
• Not locally rigid : local graph is not rigid• Locally rigid : locally rigid, but local graphs is not rigid• Globally rigid : global graph is rigid
Definition
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
multimediacomputing laboratory11
Rigidity Theory
• A graph is globally rigid if it is formed by starting from a clique of four non-coplanar nodes and repeatedly adding a node con-nected to at least four non-coplanar existing nodes
Thorem1 – In 3D
Insufficient Sufficient
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
multimediacomputing laboratory12
MAL - Distance Measurement
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
multimediacomputing laboratory13
MAL - Distance Measurement
• In simultaneous equations– Necessary Condition : unknowns – equations ≤ 0– The more we add mn, the more we have (unknowns-equations)
Calculating Distance between Two Nodes - Proposition 2
1 2
n1(a1,b1,c1) Noden2(a2,b2,c2)
1
m1(x1,y1,z1)
Mobile Node
2
m2(x2,y2,z2)
3
m3(x3,y3,z3)
Unknowns : 3 X 5 = 15Equations : 2 X 3 = 615 – 6 = 9 ≥ 0How can we solve this problem!!
obstacle
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
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obstacle
MAL - Distance Measurement
• We need restriction! – Fixed Height ( c1 = c2 (known) , z1 = z2 = z3 = 0 )
– Parallel Line ( b1 = b2 = y1 = y2 = y3 = 0)
Calculating Distance between Two Nodes – Proposition 2
1 2
n1(a1,b1,c1) Noden2(a2,b2,c2)
1
m1(x1,y1,z1)
Mobile Node
2
m2(x2,y2,z2)
3
m3(x3,y3,z3)
Unknowns : 3 X 5 = 15 – 10 = 5Equations : 2 X 3 = 65 – 6 = -1 ≤ 0We can solve this problem!!
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
multimediacomputing laboratory15
MAL - Distance Measurement
• We need restriction!– Fixed Height ( c1=c2=c3(known), z1=z2=z3=z4=z5=z6=0 )
Calculating Distance between Three Nodes – Proposition 3
1 2
n1(a1,b1,c1) Noden2(a2,b2,c2)
1
m1(x1,y1,z1)
Mobile Node
2
m2(x2,y2,z2)3
m3(x3,y3,z3)
Unknowns : 3 X 9 = 27 – 9 = 18Equations : 3 X 6 = 1818 – 18 = 0 ≤ 0We can solve this problem!!
3
n3(a3,b3,c3)
4
m4(x4,y4,z4)
5
m5(x5,y5,z5)
6
m6(x6,y6,z6)
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
multimediacomputing laboratory16
MAL - Distance Measurement
• There is no restriction– j nodes, k mobile positions– Unknowns : 3j-5
• 3D ( 3 X j ), 3 degrees of translational motion, 2 degrees of rotational motion
– Equations : k(j-3)– Required mobile positions : k =┌(3j-5)/(j-3)┐
– J = 4 then k = 7
Calculating Distance between Four Nodes – Proposition 4
1
3Node
1
Mobile Node3
2
45
67
2
4
Unknowns : 3 X 11-5 = 28Equations : 4 X 7 = 2828 – 28 = 0 ≤ 0We can solve this problem!!
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
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MAL – Movement Strategy
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
multimediacomputing laboratory18
MAL – Movement Strategy
• A) Find 4 stationary nodes that can be mea-sured from mobile
• B) Move the mobile to at least 7 spots and measure distances
• C) Compute pair-wise distances between the four stationary nodes
• D) Localize the resulting tetrahedron according to Theorem 1
Initialize
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
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MAL – Movement Strategy
• A) Pick a stationary node that has been localized but has not yet been examined by this loop
• B) Move the mobile around the stationary node, and search not-yet-localized nodes (1~3)
• C) If not-yet-localized nodes are – One, then measure distance with Proposition 2– Two, then measure distance with Proposition 3– Three, then measure distance with Proposition 4
• D) Localize it according to Theorem 1(globally rigid)
Loop
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
multimediacomputing laboratory20
Performance Evaluation
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
multimediacomputing laboratory21
Performance Evaluation
• Localization : AFL(Anchor Free Localization)• Simulation environment: Cricket• No of nodes : 24
Environment
• Real distance : Manual
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
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Performance EvaluationGraph
Graph obtained by MAL Graph after applying AFL
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
multimediacomputing laboratory23
Performance EvaluationPerformance – Error CDF
• CDF of % error between original location and estimated location
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
multimediacomputing laboratory24
Performance Evaluation
• Estimated Location after applying AFL– AFL : avoid folding problem
Performance – Estimated Locations
This spots can be lo-calized by
AFL
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
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Conclusion
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
multimediacomputing laboratory26
Conclusion
• Strong point– Very practical in indoor environment– Very accurate localization conjunction with AFL
• Weak point– Need for ultrasonic device– Need for human resource
Critique
차세대 무선 네트워크 및 보안2008 Fall CS710 Class in KAIST
multimediacomputing laboratory27
Q&A
Q&A