Transcript The coverage problem in wireless ad hoc networks

The Coverage Problem in Wireless
Ad Hoc Sensor Networks
Supervisor: Prof. Sanjay Srivastava
By,
Rucha Kulkarni
200811039
Outline
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Introduction
Types of coverage.
Computational Geometry
Background Study
Algorithm for coverage calculation
Open problems
Introduction
• Sensor node is equipped with:
– Sensing range
– Communication range
• Issues in sensor networks:
– Location discovery
– Tracking
– Deployment
– Coverage
• Coverage: Measure of Quality of Service
– How well a region is covered?
– What is the probability that an object will be detected?
– K-coverage
Types of Coverage
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Blanket coverage
Barrier coverage
Point coverage
Path coverage
Exposure
Fig.1 Blanket coverage Fig.2 Barrier coverage
Fig.3 Point coverage
Computational Geometry
• Voronoi diagrams
• Delaunay triangulations
Voronoi Diagram
Delaunay triangulation
Background Study
• [2] studies the k-coverage of wireless sensor networks
• [3] studies about the node deployment mechanisms
• [6] presents a mechanism to find paths with minimum
exposure
• [9] derives a relationship between coverage and connectivity
and integrates CCP and SPAN to guarantee coverage with
connectivity
Worst Case Coverage
• Given: A field deployed with sensors; areas I and F
• Problem: Find a maximal breach path Pb from I to F
• Pb is the path such that every point on the path is at least
breach_weight away from the sensors.
• Assumptions:
– Deterministic deployment of sensors
– Sensing ability decreases with increase in distance
Algorithm
• Construct the voronoi diagram for the given set of sensor
nodes
• Construct a graph from the voronoi diagram:
– Each vertex in the voronoi diagram corresponds to a node in the graph
– Each line segment in the voronoi diagram corresponds to an edge in the
graph
– Each edge is assigned weight equal to the minimum distance from the
closest sensor node.
• Binary search is used to find the smallest and the largest edge
in the graph using breach_weight as the threshold value
• During each iteration, BFS is used to check for the existence
of a path from I to F
Best case coverage
• Given: A field deployed with sensors; areas I and F
• Problem: Find a maximal support path Ps from I to F
• Ps is the path such that distance between every point on the
path the sensors is minimized.
• Assumptions:
– Deterministic deployment of sensors
– Sensing ability decreases with increase in distance
Algorithm
• The algorithm for the best case coverage calculation is same as
for the worst case coverage with some changes:
– The voronoi diagram is replaced with Delaunay
triangulation;
– The edges in the graph are assigned weights equal to the
lengths of the Delaunay lines;
– The breach_weight is replaced by the support_weight.
Open Problems
• To design an algorithm for the deployment of the sensor nodes
to obtain the desired coverage with minimal energy
consumption
• Coverage in three dimensional spaces
• Barrier coverage problem
References
[1] M. Cardei and J. Wu, “Coverage in Wireless Sensor Networks," Handbook
of Sensor networks, CRC Press, 2004.
[2] C.-F. Huang and Y.-C. Tseng, “The coverage problem in a wireless sensor
networks,“ ACM International Workshop on Wireless Sensor Networks and
Applications (WSNA), 2003, pp. 115-121.
[3] K. Kar and S. Banerjee, “Node Placement for Connected Coverage in
Sensor Networks,“ Proceedings of WiOpt 2003: Modeling and
Optimization in Mobile, Ad Hoc and Wireless Networks, March 2003.
[4] B. Liu, D. Towsley, “On the coverage and detectability of large-scale
wireless sensor networks," Proceedings of the Modeling and Optimization
in Mobile, Ad hoc and Wireless Networks Conference (WiOpt). (2003)
[5] S. Meguerdichian, F. Koushanfar, M. Potkonjak, M. Srivastava, “Coverage
problems in Wireless Add-Hoc Sensor Networks," Proceedings of IEEE
Infocom, vol. 3, pp. 1380-1387, April 2001.
References (contd.)
[6] S. Meguerdichian, F. Koushanfar, G. Qu, and M. Potkonjak, “Exposure in
wireless ad-hoc sensor network," ACM Mobile Computing and
Networking, pages 139-150, 2001.
[7] M.P. Singh; M.M. Gore, “A solution to sensor network coverage problem",
Proceedings of 7th IEEE International Conference on Personal Wireless
Communication (ICPWC 2005), Jan. 2005, pp.77-80.
[8] Sasa Slijepcevic, Miodrag Potkonjak, “Power Efficient Organization of
Wireless Sensor Networks", IEEE International Conference on
Communications, Helsinki, Finland,June 2001.
[9] X. Wan G. Xing, Y. Zhang, C. Lu. R. Pless. and C. Gill, “Integrated
Coverage and Connectivity Configuration in Wireless Sensor Network,"
First ACM conference on Embedded Networked Sensor Systems (SenSys'03), Los Angeles. CA, November 2003.
[10] Ming-Chen Zhao, Jiyain Lei, Min-You Wu, Yunhuai Liu, Wei Shu,
“Surface coverage in wireless sensor networks," Proceedings of 28th
conference on Computer communications, IEEE Infocom 2009, pp. 109117.
Thank You