1. KAIS T A Bidding Protocol for Deploying Mobile Sensors 발표자 : 권 영 진 Guiling Wang, Guohong Cao, Tom LaPorta The Pennsylvania State University IEEE, ICNP 03

2. Contents Introduction Voronoi diagram Bidding protocol(key concepts, remained issues) Performance evaluations Conclusion 2 / 17 A Bidding Protocol for Deploying Mobile Sensors

3. Introduction ( 1/2 ) Mobile sensor Problems : How to deploy mobile sensors efficiently? “Three distributed self-deployment protocols” (Movement-Assisted Sensor Deployment, IEEE infocom 04) Use only mobile sensor  Not cost-effective 3 / 17 A Bidding Protocol for Deploying Mobile Sensors

4. Introduction ( 2/2 ) “Bidding protocol” Key idea : static sensor + mobile sensor Coverage holes : the area that sensor cannot cover Static sensor : detection of coverage holes Mobile sensor : heal of coverage holes 4 / 17 A Bidding Protocol for Deploying Mobile Sensors Sensor circle Coverage holes Static sensor Mobile sensor Hole healing

5. Terminologies of Voronoi diagram 5 / 17 A Bidding Protocol for Deploying Mobile Sensors Voronoi cell Voronoi diagram

6. Applying Voronoi diagram to Mobile sensor Put sensor on site points  Each sensor is responsible for the sensing task in Voronoi cells  Each sensor can examine the coverage hole locally 6 / 17 A Bidding Protocol for Deploying Mobile Sensors sensor

7. Bidding protocol ( key concepts) ( 1/7 ) Important questions How to estimate coverage hole? Which mobile sensor should move to the place? Where should the mobile sensor move? Bid ( for static sensor ) estimated size of hole Base price ( for mobile sensor ) estimate of generated coverage hole after it leaves the current place 7 / 17 A Bidding Protocol for Deploying Mobile Sensors

8. Bid Estimation( in Static Sensor ) Farthest Voronoi vertex is the target location of mobile sensor Bid is the area of the inner circle 8 / 17 A Bidding Protocol for Deploying Mobile Sensors Bidding protocol ( key concepts) ( 2/7 ) Healing of most largest hole d Bid = π * ( d – sensing_range) 2  relative size of coverage hole

9. Bidding protocol ( key concepts) ( 3/7 ) Base price evaluation( in mobile sensor ) Initial value is 0 The accepted bid is a new base price Meaning of a bid and a base price 9 / 17 A Bidding Protocol for Deploying Mobile Sensors Bid: estimate of healed hole Base price : estimate of upcoming hole

10. Bidding protocol ( key concepts) ( 4/7 ) 10 / 17 A Bidding Protocol for Deploying Mobile Sensors Let’s put it all together ! Bidding protocol flows( round by round ) Service advertisement Initialization Serving Bidding Termination Construct Voronoi diagram

11. Bidding protocol ( key concepts) ( 5/7 ) Service advertisement Mobile sensor broadcasts their base price and location Base price is set to zero initially Bidding Calculate bids and target location for the mobile sensor Send bids to closest mobile sensor whose base price is lower than bids 11 / 17 A Bidding Protocol for Deploying Mobile Sensors

12. Bidding protocol ( key concepts) ( 6/7 ) Serving Mobile sensor choose the highest bids and heal coverage holes Accepted bids becomes new base price Termination If base price of all mobile sensor is higher than bids, then terminate 12 / 17 A Bidding Protocol for Deploying Mobile Sensors

13. Bidding protocol ( key concepts) ( 7/7 ) 13 / 17 A Bidding Protocol for Deploying Mobile Sensors Mobile sensor Static sensor 93% coverage at round 5 40 sensors, 12 mobile sensors 82% coverage

14. Performance evaluations ( 1/3 ) Evaluation methodology Main cost Number of sensor Number of round Environment Ns-2 simulator 40 sensors and 10 independent experiments Some considerations Trade off between cost and coverage Cost ratio between the mobile sensor and the static sensor 14 / 17 A Bidding Protocol for Deploying Mobile Sensors

15. Performance evaluations ( 2/3 ) 15 / 17 A Bidding Protocol for Deploying Mobile Sensors Random deployment : just use static sensor Bidding protocol : static sensor + mobile sensor VEC algorithm : mobile sensor Random deployment Bidding protocol VEC algorithm Trade off The more mobile sensor are used, The better coverage is obtained But the sensor cost will be increased

16. Performance evaluations ( 3/3 ) 16 / 17 A Bidding Protocol for Deploying Mobile Sensors

17. Conclusions Voronoi diagram can be applied to a sensor network using a greedy heuristic method Mixture of a static sensor and a mobile sensor can achieve a good balance between coverage and cost 17 / 17 A Bidding Protocol for Deploying Mobile Sensors

18. Extra ( 1/4 ) Duplicate healing 18 / 17 A Bidding Protocol for Deploying Mobile Sensors

19. Extra ( 2/4 ) Duplicate healing detection 19 / 17 A Bidding Protocol for Deploying Mobile Sensors A B Broadcast Check if base price of A > base price of B If yes, run detection algorithm If detected, set base price of A to zero

20. Extra ( 3/4 ) Detection Algorithm Detecting threshold = π * ( d min – sensing_range) 2 d min : Distance to closest neighbor IF ( detecting threshold < new base price || d min < sensing_range ) THEN duplication occurs 20 / 17 A Bidding Protocol for Deploying Mobile Sensors

21. Extra ( 4/4 ) 21 / 17 A Bidding Protocol for Deploying Mobile Sensors A,B is mobile sensor Snapshot in the middle of round N f ’s base price is calculated without consideration of N e at N f Detecting threshold < New base price New base price of B d min Why Detecting threshold < New base price?