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Energy-Efficient PON with Sleep-Mode ONU Progress, Challenges, and Solutions

Energy-Efficient PON with Sleep-Mode ONU Progress, Challenges, and Solutions. Speaker: Shieh-Chieh Chien Advisor: Dr. Ho-Tin Wu 2013/09/23. Outlines. Basic knowledge Background Current progress Challenges in Energy-Saving PON SLA-Based Energy-Efficient Scheduling Scheme

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Energy-Efficient PON with Sleep-Mode ONU Progress, Challenges, and Solutions

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  1. Energy-Efficient PON with Sleep-Mode ONU Progress, Challenges, and Solutions Speaker: Shieh-ChiehChien Advisor: Dr. Ho-Tin Wu 2013/09/23

  2. Outlines • Basic knowledge • Background • Current progress • Challenges in Energy-Saving PON • SLA-Based Energy-Efficient Scheduling Scheme • Put ONU into sleep mode • Guard time • Sleep time state transition • ReservingslotsforsleepingONU • High-priority frame come to the sleeping ONU • Compare graph • Conclusion • References

  3. Basic knowledge • PON=Passive Optical Network • OLT = Optical Line Terminal • ONU = Optical Network Units

  4. Basic knowledge(Cont.) • Control message • Grant(Gate) • Downstream direction(broadcast) • Allows an ONU to start sending data. • Include ONU_ID, window size(in bytes) • Request(Report) • Upstream direction • Include how many bytes in ONU’s buffer.

  5. Background • The subscribers’ ever increasing demands for bandwidth. • Thelinerate increase in the access network and it will brings more powerconsumption. • PONconsumes significantly less energy than its counterparts based on copper, wireless, or active optical technologies.

  6. Current progress • Methods proposed for power saving so far: • Better IC design • Power shedding of non-essential parts • Slowing down link rate • Putting network elements in sleep mode

  7. Current progress(Cont.) • No ONU energy saving function is included in the EPON standard. • Power saving schemes in different domain • GPON • ONU shedding, dozing, and sleeping • Sleep mode also used in wireless communication • IEEE 802.3az Energy Efficient Ethernet(EEE) • Low Power Idle (LPI) mode

  8. Challenges in Energy-Saving PON • WhendotheONUgotosleeporwakeup? • > Trade-off between • powersavingvs.network performance • Frequent mode switching • > Energy wasted in wake up process • > Extra Overhead (2 ms) from sleep to active

  9. SLA-Based Energy-Efficient Scheduling Scheme • According to experienced traffic to adjust the sleep time. • Allowing ONU to quit sleep mode before the predetermined sleep time is up in order to send high-priority packets. • Add an extra guard time at the end of the active period. • Proposal is within the IEEE P802.3ah/av control schemes and requires minor changes in the control signal flow.

  10. SLA-Based Energy-Efficient Scheduling Scheme(Cont.) • The scheduling scheme categorizes packets into two classes with different SLAs. • High-priority class is expedited forwarding(EF) • Low-priority class is best effort(BE) • Three-bit priority value to store in the frame header defined by IEEEP802.1p. • Preemptive queues are used at both OLT and ONU. • Credit-based bandwidth allocation is used by the OLT to assign bandwidth dynamically.

  11. Put ONU into sleep mode • When ONU into sleep mode • Stop sending REPORT • All low-priority frames will be stored in its buffer until sleep period expires. • Pros and cons • In worst-case all the low-priority frames experience an extra delay. • High-priority frames in upstream direction will be guaranteed a small delay.

  12. Guard time • If (after the end of the transmission on both directions)then {wait extra guard time} /*This time is used to identify whether the current traffic burst is over or not.*/

  13. Sleep time state transition

  14. ReservingslotsforsleepingONU

  15. High-priority frame come to the sleeping ONU

  16. High-priority frame come to the sleeping ONU(Cont.) • In upstream direction • The frameh is from the users, the ONU will wake up immediately. • In downstream direction • OLT has no means to inform the ONU. →frameh still encounter delay. ─ Delay could be alleviate → implement a cross-layer design

  17. Compare graph

  18. Conclusion • To design a energy-efficient PONs with sleep-mode ONUs, the challenge is to find the optimal scheduling scheme. • SLA-based energy-efficient scheduling scheme could meet these challenges and solve the problem of frequent mode switching. • Adjusts the sleep time according to traffic • Extra guard time before into sleep period • Can quit sleep mode for high-priority frames

  19. References • [1] L. Shi, B. Mukherjee, and S. S. Lee, "Efficient PON with Sleep-Mode ONU: Progress, Challenges, and Solutions," IEEE Network Magazine, vol. 26, no. 2, 2012, pp. 36-41.

  20. Thanks for listening • Q&A

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