1. Decentralized Energy-Conserving and Coverage-Preserving Protocols for Wireless Sensor Networks Chi-Fu Huang, Li-Chu Lo, Yu-Chee Tseng, and Wen-Tsuen Chen Department of Computer Science and Information Engineering National Chiao-Tung University Department of Computer Science National Tsing-Hua University IEEE International Symposium on Circuits and System (ISCAS ’ 05)

2. Outline Introduction 1-Coverage-Preserving Protocol Basic Energy-based Simulation Results Conclusion

3. Introduction This paper proposed protocols are based on a model similar to that of [8], but improve it First, reduce the computational complexity Second, balance sensors ’ energy expenditure [8] Differentiated surveillance for sensor networks. (SenSys 2003)

4. Introduction Goals Provide an approach for nodes to decide their sleep/work mode schedules: Guarantee Full-coverage Redundant nodes go to sleep to save energy and extend system lifetime

5. Introduction -Differentiated surveillance for sensor networks Work/Sleep schedule for a single point A B C Node A Node B Node C 0 100 3070 1060 5 45 time Awake Asleep Point X

6. 10 Introduction -Differentiated surveillance for sensor networks Work/Sleep schedule for a single point A B C Node A Node B Node C Awake 0 100 3070 60 5 45 time Asleep Point X Point x is covered by at least one node ’ s sensing area at any time

7. t A C B Introduction -Differentiated surveillance for sensor networks Point X t 0 100 105 20 refC 40 refA 90 refB 120 refC 100 3065 5 105 T front T end Reference randomly selected from [0, T) Each node broadcasts tuple (location, reference)

8. Introduction -Differentiated surveillance for sensor networks Sensing Phase Init Phase ref Round 0 (Duration T) Round 1 Round n ……… Work Schedule: [n×T + ref – T front ﹐ n×T + ref + T end ] ref

9. D C B A Introduction -Differentiated surveillance for sensor networks Schedules for All Grid Points E Grid Points

10. Introduction -Differentiated surveillance for sensor networks

11. 1-Coverage-Preserving Protocol -Assumption Sensors S i, i = 1, …,n Location ( X i, Y i ) Sensing Range r i Each Sensor can switch between the active mode and the sleeping mode Two sensors S i and S j are neighbors If they have non-empty overlapping sensing region Sensors can communicate with his neighbors

12. 1-Coverage-Preserving Protocol – Basic The structure of sensors ’ working cycles 1. Location ( X i, Y i ) 2. Sensing range r i 3. Reference time Ref i

13. 1-Coverage-Preserving Protocol – Basic Initialization phase Each sensor S i broadcasts a HELLO packet after random backoff Location ( X i, Y i ) Sensing range r i Reference time Ref i randomly selected from [0, T rnd ) Each sensor S i can calculate it own working schedule in the sensing phase To calculate Front i and Back i

14. 1-Coverage-Preserving Protocol – Basic Each sensor ’ s Front i and Back i should be carefully selected to ensure that the sensing area is sufficiently covered To achieve this goal, we use intersection points If all intersection points in the target area A are covered by any sensor ’ s sensing range, the target area A is sufficiently covered

15. m 1-Coverage-Preserving Protocol – Basic t t 0 2 Ref 1 9 Ref 2 11 Ref 3 20 5.5 16.5 Front 1 =5.5 Back 1 =3.5 20 n q S1S1 S3S3 S5S5 S2S2 S4S4 p r Schedule for p Front 1 211205.5 92203.5 0

16. 1-Coverage-Preserving Protocol – Basic

17. 1-Coverage-Preserving Protocol – Energy-base Each sensor S i is aware of its current remaining energy, denoted as E i Each sensor S i broadcasts its E i in the HELLO packet

18. 1-Coverage-Preserving Protocol – Energy-base Front i and Back i of the sensor S i are chosen based on E i

19. Simulation Result 100 x 100 square are 150 sensors, randomly generated Sensing range 25 A working cycle (T w_cycle ) include 5 rounds To set up sensors’ initial energies Can active from 1 to 50 complete rounds in randomly selected manner

20. Simulation Result

22. Conclusion The paper protocols improve the results in several sense Significantly reduce the computational complexity Use intersection points Further balance sensors ’ energy expenditure Use sensors ’ remaining energy

23. Thank you !!