Maximizing Angle Coverage in Visual Sensor Networks Kit-Yee Chow, King-Shan Lui and Edmund Y. Lam Department of Electrical and Electronic Engineering The University of Hong Kong Pokfulam Road, Hong Kong, China ICC 2007

2 Outline Introduction Network Model Protocol Simulation Conclusions

3 Introduction Wireless sensor network  Disaster management  Habitat monitoring

4 Introduction Sensor nodes  Battery operated  Non-rechargeable

5 Introduction Sensor nodes  Message transmission has been shown to be the major source of energy dissipation in sensor networks.  In order to prolong the system lifetime, we should keep the transmission load as small as possible.

6 Introduction Coverage problem  Target coverage  Area coverage  Angle coverage Sensor nodes Object

7 Introduction Angle coverage  Resolution  Cover different sides of the object

8 Motivation A trivial way to preserve the widest angles of view is to gather all the images.  Non-energy efficient  Many redundant images  Heavy transmission load

9 Goal Identify a minimum set of sensors such that  Fulfill the resolution requirement  Preserving all the angles of view

10 Network Model Sensor nodes  Camera-equipped Field-of-view (FOV) Do not have the capability of pan, tilt and zoom Camera orientation  Static  Know its physical location by means of GPS or a localization algorithm

11 Relationship Between Image Resolution And Node Distance >x resolution decreases

12 Angle Coverage Sensor nodes Object

13 Protocol Candidate Identification  Pruning images of low resolution Image Selection  Identified images that cover all angles of view

14 Image Selection The set of sensors with  Smallest size  Preserving all the captured range

15 Image Selection {1,4,7} {2,3,5,6}

16 Image Selection {1,4,7}

17 Image Selection {2,3,5,7,8,1}

18 Image Selection Determine whether there is any angle of view that is covered by one sensor {1,3,5,7,8}

19 Image Selection Default member  Sensor node must be in a minimum cover if it covers an angle that is not covered by others.  Announcing to its neighbor that it is selected and then starts to identify the next sensor.

20 Image Selection Default member

21 Image Selection Default member {1,3,5,6,9}

22 Image Selection When the sensors cannot cover 360° {1,3,5,7}

23 Simulation MATLAB Camera: 512x512 pixels Image resolution: κ

24 Simulation

25 Simulation

26 Simulation

27 Conclusions Angle coverage in visual sensor network  Maximizing angle coverage  Minimum number of images to be sent  Fulfilling the image resolution requirement

28 Thank you!