1. Data-Centric Energy Efficient Scheduling for Densely Deployed Sensor Networks IEEE Communications Society 2004 Chi Ma, Ming Ma and Yuanyuan Yang

2. Outline  Introduction  Data-Centric Energy Efficient Scheduling Communication-Centric Initialization Phase Characteristics of the traffic in sensor networks Data-centric scheduling phase  Power Shutdown Scheme  Performance Comparisons with Existing Protocol  Conclusion

3. Introduction  Previous work: Predictive power management strategy  Only highly correlated requests can benefit from it Markov Chain method based on historic data analysis  [7] point out that this is not suitable for today ’ s low energy and low computation sensor Power mode scheduling  Does not distinguish between the routing data and the sensing data

4. Introduction  All previous work assume that both sensing and routing packets come as homogeneous traffic  They propose DCe2S (Data-centric energy efficient scheduling) to minimizing the power dissipated under heterogeneous packet traffic

5. Data-Centric Energy Efficient Scheduling  DCe2S protocol consists of two phases: 1. Communication-centric initialization phase 2. Data-centric scheduling phase

6. Communication-Centric Initialization Phase  Determine node ’ s lengths of sleep according to sensor density (not uniform)  IAR Energy dissipation Probability to lose packet Higher density (after CCI)

7. Communication-Centric Initialization Phase  :the probability the packet is not lose of node p  :numbers of neighbor of node k  Given, if any routing node i of sending node p has that,then the can be guaranteed at sending node p P IARp

9. Characteristics of the traffic in sensor networks  There are two types of data: Sensing packets Routing packets  Previously proposed protocols assume that both types of traffic follow are homogeneous Poisson distribution  Apparently, it cannot model real traffic (ex. traffic monitoring)  Even the sensing traffic is homogeneous, the routing traffic cannot not be homogeneous

10. Characteristics of the traffic in sensor networks Path length Sensing traffic

11. Characteristics of the traffic in sensor networks  There are k path  Traffic out of Di :  t : latency for each node  Consider traffic from A  Consider traffic from both A and C

12. Characteristics of the traffic in sensor networks  When sensing traffic is heterogeneous Poisson traffic  Suppose A has sensing rate of  When,the case is equivalent to A broadcasts packets at homogeneous rate, and A` broadcasts after t1  And is the same

13. Data-Centric Scheduling Algorithm  Use exponentially weighted average time to combine and to obtain  is a threshold means a sudden change  A sliding window with size W is used to cache the recent packet arrival intervals

14. //exponentially weighted //average of the window

15. Power Shutdown Scheme  DCS algorithm uses the shut-down scheme in [8]  The shut-down latency for turning on/off : Sensing unit30ms Transmitter5ms Receiver5ms

16. Power Shutdown Scheme

17. Derive a set of sleep time threshold{Tth,k} if ti<Tth,k will result net energy loss next event

18. Performance Comparisons with Existing Protocol  The Time Out Protocol Node switches to sleeping blindly for a time period of T out  The Greedy Protocol Without any power control protocol  The Power Mode Scheduling Protocol (PMS)

19. Power dissipation (homogeneous) 100ms 500ms

20. Packet Loss Rate (homogeneous) 61.4% better than Greedy 31% better than PMS Unstable because of predict

21. Heterogeneous traffic  1000 packets  First phase: 200 packets  Second phase: 400 packets  Third phase: 400 packets  Packet Lost Rate

22. Power dissipation (heterogeneous)

23. Packet Loss Rate (heterogeneous) Events are not uniformly distributed

24. Conclusions  They first prove the routing traffic is heterogeneous with Poisson sensing traffic  Then proposed a well defined power model to extend the lifetime without compromising their performance  Presented DCe2S in this paper and try to achieve maximum lifetime