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On the Coverage Problem in Video-based Wireless Sensor Networks

On the Coverage Problem in Video-based Wireless Sensor Networks. Stanislava Soro Wendi Heinzelman University of Rochester. Outline. Motivation Problem statement Overview of DAPR DAPR in video-based WSNs Simulation results Conclusions. Motivation. Telepresence application for VWSN

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On the Coverage Problem in Video-based Wireless Sensor Networks

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  1. On the Coverage Problem in Video-based Wireless Sensor Networks Stanislava Soro Wendi Heinzelman University of Rochester

  2. Outline • Motivation • Problem statement • Overview of DAPR • DAPR in video-based WSNs • Simulation results • Conclusions BASENETS'05

  3. Motivation • Telepresence application for VWSN • enables user to experience being fully present at a physically remote location • network consists of wireless nodes equipped with very low-power cameras • user can navigate and virtually move around in the monitored space BASENETS'05

  4. Motivation (II) • Distinct features of video-based WSN over traditional WSN • Very large amount of highly correlated data • Capturing images of objects that are not necessarily in camera’s vicinity • Sensing range is replaced with FoV (field of view) BASENETS'05

  5. Problem of interest… • Coverage preservation in WSNs: • PEAS, DAPR, CCP…. • How do already existing coverage protocols for WSNs behave in video-based WSNs? • We assume floorplan monitoring – monitoring of scene in one plane • Each point of monitored area should be covered by at least one camera • We analyze how an application-aware routing protocol (DAPR) behaves in this design space BASENETS'05

  6. (x,y) Overview of DAPR in WSN • DAPR-Distributed Activation based on Predetermined Routes • Coverage preserving protocol that avoids the data routing through critical nodes • Proposes application-aware approach – each node’s importance for sensing application is evaluated • C(Sj) – area monitored by sensor Sj • Monitored area is divided into grid, where the center of each grid cell is given as (x,y) • Total energy for monitoring location (x,y): BASENETS'05

  7. S3 E(S3)=5 S4 E D E(S4)=10 C G S1 F B E(S1)=1 A S2 E(S2)=2 Overview of DAPR in WSN (II) Application cost of node S1 BASENETS'05

  8. Overview of DAPR in WSN (III) • Application cost: • Link cost between two nodes: • Cost of a route from node to sink: BASENETS'05

  9. DAPR in camera-based WSNs • Two planes • Cameras’ plane: location of point given as (x,y) • Cameras’ FoV plane: location of point given as (xc,yc) BASENETS'05

  10. DAPR in camera-based WSNs (II) • Every location (xc,yc) on monitoring plane characterized by total energy: • Final application cost: • Total routing cost for every camera: BASENETS'05

  11. Traditional energy-aware routing • Willingness of every node to route data: • This cost does not consider the importance of a node for sensing application BASENETS'05

  12. Comparison of application-aware routing in WSN and video-based WSN Traditional wireless sensor network Video-based wireless sensor network BASENETS'05

  13. Requested part of the scene determines the locations of all potentially active sensor nodes The application cost tells us how redundantly the node is covered how important node is as a router BS Application-aware routing in wireless sensor networks BASENETS'05

  14. Mismatch between cameras’ physical positions and cameras’ FoV Here, the application cost evaluates the node: only from the coverage perspective but NOT from the routing perspective Example: a node can be well covered (small application cost), but located in scarcely deployed area – makes it important as a router BS network’s plane scene plane Application-aware routing in video-based WSNs BASENETS'05

  15. Application-aware routing in video-based WSN (II) • Hotspot problem appears more easily • Potentially active nodes can be far from each other • Select to be active a node with smallest cumulative path cost – usually node closest to the base station • Energy-aware cost outperforms application-aware cost • Balanced energy spent among the nodes – prolongs the lifetime of each node • The loss of nodes is more uniform over the area BASENETS'05

  16. Combined application and routing cost • Every camera node validated through two separate cost functions BASENETS'05

  17. Combined application and routing cost • Reduces the energy consumption, compared to application-aware routing • With a change in number of nodes, the same relation between three protocols persist BASENETS'05

  18. Conclusions • Application-aware routing protocol gives different results in traditional and video-based WSNs • Found that coverage and routing problem exist as two separate problems in video-based WSNs • Further study of this problem • Explore further combined cost function • Explore how other coverage preserving protocols behaves in video WSNs • Three dimensional coverage problem • Consider collaboration of cameras • Consider the ability of cameras to capture image with different resolution BASENETS'05

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