KAIST
Adaptive Triangular Deployment Adaptive Triangular Deployment Algorithm Algorithm
for Unattended Mobile Sensor Networksfor Unattended Mobile Sensor Networks
Suho Yang(September 4, 2008)
Ming Ma, Yuanyuan Yang
IEEE Transactions On Computers 2007
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ContentsContents
Introduction
Assumption
Ideal Node Layout for Maximum Coverage
Two Triangular algorithmsBasic Triangular Algorithm
ATRI : Adaptive Triangular algorithm
Performance Evaluation
Conclusion
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Wireless Sensor NetworksApplications: 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
IntroductionIntroduction
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Deployment problem for WSNProblem 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
IntroductionIntroduction
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AssumptionsAll sensors are mobile sensors
All sensors have the same capacities (=sensing range, energy, …)
Omni-directional sensing
No global information
No location-awarenessEach sensor only estimate the relative locations to neighbors
Initially, all sensors are randomly deployed
AssumptionAssumption
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Problem 1: “Where to place sensors?”Problem 1: “Where to place sensors?”- Ideal Node Layout for Maximum Coverage- Ideal Node Layout for Maximum Coverage
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The optimal node layout for the maximum no-gap coverage
Equilateral triangulation
Ideal Node Layout for Maximum CoverageIdeal Node Layout for Maximum Coverage
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ProofThe maximum value of can be obtained when
In this case, the lengths of all three edges =
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Ideal Node Layout for Maximum CoverageIdeal Node Layout for Maximum Coverage
2
3r
r6
r3
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Problem 2: “How to move sensors?”Problem 2: “How to move sensors?”- Basic Triangular Deployment Algorithm- Basic Triangular Deployment Algorithm
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Main ideaEach 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 AlgorithmBasic Triangular Deployment Algorithm
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Adjusting the distance between neighbors Notation
Basic Triangular Deployment AlgorithmBasic Triangular Deployment Algorithm
rR 3where r = sensing range
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Adjusting the distance between neighbors (cont.)
Basic Triangular Deployment AlgorithmBasic Triangular Deployment Algorithm
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Adjusting the distance between neighbors (cont.)
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Adjusting the distance between neighbors (cont.)
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Basic Triangular Deployment AlgorithmBasic Triangular Deployment Algorithm
1v
2v
3v
4v
5v
6v
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Algorithm
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Snapshots of the execution
Basic Triangular Deployment AlgorithmBasic Triangular Deployment Algorithm
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Reducing node oscillation(1) Distance threshold strategy
Constant threshold
Variable threshold
Basic Triangular Deployment AlgorithmBasic Triangular Deployment Algorithm
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Reducing node oscillation(2) Movement state diagram strategy
Basic Triangular Deployment AlgorithmBasic Triangular Deployment Algorithm
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Problem 2: “How to move sensors?”Problem 2: “How to move sensors?”- - ATRI: Adaptive Triangular Deployment AlgorithmATRI: Adaptive Triangular Deployment Algorithm
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Additional consideration 1. Avoiding obstacles and boundaries
2. Non-uniform deployment
ATRI: Adaptive Triangular Deployment ATRI: Adaptive Triangular Deployment AlgorithmAlgorithm
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1. Avoiding obstacles and boundariesDetect them with an ultrasonic obstacle-detecting module
And abstract them as virtual nodes
ATRI: Adaptive Triangular Deployment ATRI: Adaptive Triangular Deployment AlgorithmAlgorithm
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Snapshots of the execution for the environment with obstacles
ATRI: Adaptive Triangular Deployment ATRI: Adaptive Triangular Deployment AlgorithmAlgorithm
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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 ATRI: Adaptive Triangular Deployment AlgorithmAlgorithm
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Snapshots of the execution for non-uniform deployment
ATRI: Adaptive Triangular Deployment ATRI: Adaptive Triangular Deployment AlgorithmAlgorithm
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Performance EvaluationPerformance Evaluation
Measurement of performanceDeployment 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]
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Performance EvaluationPerformance Evaluation
Total coverage area gets larger
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Performance EvaluationPerformance Evaluation
Average moving distance gets smaller
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The optimal node layout for maximum coverageEquilateral triangulation (the length of each side equals )
Basic Triangular AlgorithmDivides the transmission circle into six sectors and adjust the relative distance between neighbors
For reducing node oscillationDistance threshold strategy
Movement state diagram strategy
Adaptive Triangular algorithmAvoiding obstacles and boundaries
Abstract them as virtual nodes
Non-uniform deploymentSet a shorter sensing range in important area
ConclusionConclusion
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The lack of mentions aboutRelation between communication range and sensing range
Definition of some notations
The meaning of some equations
Termination condition
No consideration aboutCommunication overhead
Deployment time
Impact of threshold
Synchronization and collision
DiscussionDiscussion
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Thank youThank you
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[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
ReferencesReferences
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What is Delaunay Triangulation?
Appendix A: Delaunay TriangulationAppendix A: Delaunay Triangulation
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Minimum average moving distance
Proof
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Appendix B: Minimum average moving Appendix B: Minimum average moving distancedistance