1. An Energy-Efficient MAC Protocol for Wireless Sensor Networks Qingchun Ren and Qilian Liang Department of Electrical Engineering, University of Texas at Arlington IEEE Globecom 2005

2. Outline Introduction Introduction Protocol description and discussion Protocol description and discussion –Basic parameter design –Phase switch schedule –Time-slot assignment Simulations Simulations Conclusions Conclusions

3. Introduction 1. Most energy-efficient MAC protocols assume perfect network time synchronization –Clock drifts exist

4. Introduction 2. The duration of power on/off is seldom discussed 3. Traffic arrival rate for different nodes at different time is fluctuating

5. Goals of This Paper Propose an energy-efficient MAC protocol to Propose an energy-efficient MAC protocol to –Remove tight dependency on time synchronization –Apply fuzzy logic rescheduling scheme –Compensate clock drifts

6. ASCEMAC (Asynchronous Energy- Efficient MAC Protocol)

7. ASCEMAC Protocol Model 1.TRFR-Phase: cluster members transmit message to cluster head 2.Schedule-Phase: cluster head broadcasts it ’ s scheduling 3.On-Phase: two of the cluster members communicate directly 4.Off-phase: all nodes turn their transceivers off

8. TRFR Message Format Information for a cluster head to determine the scheduling

9. Parameter Design Combine T n : on phase duration T f : off-phase duration T d : slot time W max : maximum waiting time λ i : traffic arrival rate for node i K i : buffer size

10. Parameter Design The goal of adjusting parameters The goal of adjusting parameters –Extend the power off time –Adjust the data packet waiting time to an acceptable value

11. Schedule Message Format

12. Interval of Schedule Broadcast ξ i is the interval adjusting function ξ i is the interval adjusting function Three parameters are used to design ξ i Three parameters are used to design ξ i –Ante1: ratio of nodes having overflow buffer –Ante2: ratio of failure transmission rate –Ante3: ratio of unsuccessful transmission rate(?)

13. Using Fuzzy Function The authors mention that ξ i is defuzzified by The authors mention that ξ i is defuzzified by E. H. Mandani, “ Application of fuzzy logic to approximate reasoning using linguistic systems ”, IEEE Trans. On system, Man, and Cybernetics, vol. 26, no. 12, pp. 1182-1191, 1977.

14. Time-slot assignment △ t 1 : time difference between nodes T s,min : the least time needed to detect the synchronization information Successful transmission rate

15. Rules for Time Slot Allocation Ante1: traffic arrival rate Ante1: traffic arrival rate Ante2: unsuccessful transmission rate Ante2: unsuccessful transmission rate

16. Simulation

17. Simulation Environment SimulatorOPNET Area 100m x 100m Radio range 30m Symbol rate 40 Ksps Data frame length 1024 bits Clock drift range 1 to 100us

18. Successful Transmission Rate

19. Average Waiting Time

20. Average Energy Utility

21. Successful Transmission Rate

22. Node Density Adaptation

23. Traffic Strength Adaptation

24. Conclusions ASCEMAC acquires the optimal values of essential algorithm parameters ASCEMAC acquires the optimal values of essential algorithm parameters –Ensure average successful transmission rate –Decrease the data packet average waiting time –Reduce energy consumption

25. Thank you!!

26. Antes

27. Rescheduling Broacast

28. Slot Assignment