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The Coverage Problem in Wireless Ad Hoc Sensor Networks. Supervisor: Prof. Sanjay Srivastava By, Rucha Kulkarni 200811039. Outline. Introduction Types of coverage. Computational Geometry Background Study Algorithm for coverage calculation Open problems.
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The Coverage Problem in Wireless Ad Hoc Sensor Networks Supervisor: Prof. Sanjay Srivastava By, Rucha Kulkarni 200811039
Outline • 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 • Blanket coverage • Barrier coverage • Point coverage • Path coverage • Exposure Fig.2 Barrier coverage Fig.1 Blanket 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 (Sen-Sys'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. 109-117.