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To Sync or Not to Sync in Power Saving?

To Sync or Not to Sync in Power Saving?. Ten H. Lai. Essential Fundamental Simple Effective Fresh. Zen ( 禪 ) Networking. Problems Protocols. Problem, Problem, Problem!. ???. Energy Efficiency. Done at every level from physical to application. Energy-efficient routing.

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To Sync or Not to Sync in Power Saving?

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  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

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