1. Junchao Ma +, Wei Lou +, Yanwei Wu *, Xiang-Yang Li *, and Guihai Chen & Energy Efficient TDMA Sleep Scheduling in Wireless Sensor Networks + Department of Computing The Hong Kong Polytechnic University * Department of Computer Science Illinois institute of Technology & State Key Lab of Novel Software Technology Nanjing University IEEE INFCOM 2009

2. Outline Introduction System Model Problem Formulation Contiguous Link Scheduling Centralize Distributed Simulations Conclusions

3. Introduction The energy consumption on wireless sensors Idle listening Receiving Transmitting Idle listening consumptions almost the same amount of energy as required for receiving Sleeping Scheduling

4. Introduction TDMA MAC protocol is used to avoid interference No contention-introduced overhead Collision Free To guarantee a deterministic delay bound The energy consumption on state transition

5. Introduction Motivation The energy consumption on states transition Interference-free TDMA sleep schedule problem Goals Interference-free scheduling Contiguous link scheduling to reduce frequency of state transition If the topology is a tree, a node only needs to start up twice in a period Receiving data Transmitting data

6. System Model Network Model Communication Graph Sensors Data collection algorithm

7. System Model Interference Model r R R No transmission in R

8. System Model Energy Model 2.1ms 22 μ J

9. Problem Formulation

11. Merged Conflict Graph Communication Graph Conflict Graph

12. Merged Conflict Graph L a (1) Lc(1)Lc(1) Lc(1)Lc(1) Ld(1)Ld(1) Ld(1)Ld(1) Lb(2)Lb(2) Lb(2)Lb(2)

13. Centralized Algorithm

14. 哈哈 cc ViVi VjVj VkVk r R r r R-r (R-r )/2

15. Centralized Algorithm

17. Centralized Algorithm with Spatial Reuse l1l1 l1l1 l3l3 l4l4 l5l5

18. 1 1 1 1 1 1 1 1 1 n-consecutive rows

19. Centralized Algorithm with Spatial Reuse Recursive Backtracking

20. Centralized Algorithm with Spatial Reuse Recursive Backtracking 1 1 1

21. Centralized Algorithm with Spatial Reuse Recursive Backtracking 1 1 1 0 0

22. Centralized Algorithm with Spatial Reuse Minimum Conflicts Heuristic

23. Distributed Algorithm

24. Simulation Transmission Range 15m Interference Range 30m Network Size 100m* 100m Compare Algorithm Centralize Recursive Backtracking Distributed Distributed-delay Degree-Bound Data collection BFS DAG Graph

25. Simulation BFS Tree

26. Simulation DAG Graph

27. Simulation BFS Tree

28. Simulation DAG Graph

29. Simulation BFS Tree

30. Simulation DAG Graph

31. Simulation BFS Tree

32. Simulation DAG Graph

33. Conclusions A new interference-free TDMA sleep scheduling is proposed A sensor only starts up once to receive all the data from its neighbor Saving the energy and time costs on state transition