To Sync or Not to Sync in Power Saving?

1. To Sync or Not to Sync in Power Saving? Ten H. Lai

2. Essential Fundamental Simple Effective Fresh Zen (禪) Networking Problems Protocols

3. Problem, Problem, Problem! ???

4. Energy Efficiency • Done at every level from physical to application. • Energy-efficient routing. • Energy-efficient MAC. • Energy-efficient everything.

5. Power Saving at MAC Layer Beacon interval awake sleep Beacon window ATIM window

6. Time Sync Is Necessary/Important • Really? • What if it is difficult or impossible to synchronize clocks?

7. To sync or not to sync? • Yes global synchronization • Nono synchronization • Partially local synchronization

8. No Synchronization • “Power-Saving Protocols for IEEE 802.11-BasedMulti-Hop Ad Hoc Networks” • INFOCOM 2002 • Yu-Chee Tseng, Chih-Shun Hsu, Ten-Yueng Hsieh • National Chiao-Tung University

9. No Synchronization (0) • Basic idea: nodes have to awake for long enough time. • Extreme case: awake all the time.

10. No Synchronization (1) • Dominating-Awake-Interval • Awake > BI/2 + BW

11. No Synchronization (2) • Periodical-Fully-Awake-Interval

12. No Synchronization (3) • Quorum-based

13. Local Synchronization • “An Energy-Efficient MAC Protocol for WirelessSensor Networks” • INFOCOM 2002 • Wei Ye, John Heidemann, Deborah Estrin • UCLA

14. Local Synchronization (0) • Offset 10:10 10:04 -0:01 0:05 0:01 10:09 - 0:05

15. Local Synchronization (1) • Awake/sleep schedules A B C 1:00 2:00 3:00

16. Time Synchronization in 802.11 A B C 1:00 2:00 3:00

17. Local Synchronization (2) A 0:09 0:07 B 0:04 0:05 C 1:00 2:00 3:00

18. Local Synchronization (3) A B C

19. Local Synchronization (4) • Nodes are free to choose their schedules • Or synchronize with others • Or adopt multiple schedules

20. Local Synchronization (3) A B C D

21. Communications A B C

22. To sync or not to sync? • Yes (global sync) • No (no sync) • Partially (local sync) • Which one?

23. Analysis of energy saving (1) • No data traffic • Parameters

24. Analysis of energy saving (2)

25. Global Synchronization: pro and con • Best performance in energy saving • Have to assume: • Formation: MANET initiated by a single node. • Connectivity: MANET remains connected. • Overhead

26. No Synchronization – pro and con • Simple -- no need for clock sync • Less efficient in power saving • Any other disadvantages?

27. No Synchronization: Analysis • B has a packet for A in interval 14. • Q: When should B send it? • In every blue. • Or when blue meet gray. • Q: When will blue meetgray  ?

28. 金剛經的智慧 • 所謂 … 即非 … 是名 … • The so calledno synchronization is not no synchronization; it’s named no synchronization.

29. No Synchronization: Analysis

30. No Synchronization – pro andcon • Less efficient in power saving • Simple -- no need for clock sync • Simpler – clock sync is simpler and more scalable, but less energy efficient ?

31. Time Sync in the “No Sync” Scheme • Simpler, more scalable, less energy efficient Beacon window ATIM window

32. Local Synchronization: proand con • Infocom 2002, Ye & Heidemann & Estrin • Multiple schedules • Inefficient with multiple schedules • Many issues unaddressed

33. To sync or not to sync? • Yes (global sync) • No (no sync) • Partially (local sync) • Which one? Normal situation Neighbor discovery Transient situation All of them

34. Proposed Protocol • Normally, use the global sync scheme. • Switch to the no sync scheme when necessary (for neighbor discovery). • Use the partial sync scheme while merging. ?

35. Happy Ending To sync or not to sync? • Yes (global sync) • No (no sync) • Partially (local sync) All of them

36. Problem, Problem, Problem! Power saving ??? MAC Awake-sleep global no partial sync