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Grant Scheduling for EPONs Considering Varying RTTs and Grant Window Sizes

Grant Scheduling for EPONs Considering Varying RTTs and Grant Window Sizes. 施清棋 2011-03-02. System Model. Offline DBA framework Grant Sizing & Grant Scheduling Fixed Guard Time between Transmission Windows Ignore GRANT message and Scheduling Time.

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Grant Scheduling for EPONs Considering Varying RTTs and Grant Window Sizes

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  1. Grant Scheduling for EPONs Considering Varying RTTs and Grant Window Sizes 施清棋 2011-03-02

  2. System Model • Offline DBA framework • Grant Sizing & Grant Scheduling • Fixed Guard Time between Transmission Windows • Ignore GRANT message and Scheduling Time

  3. The Composition of Packet Delay • : From Generating to Scheduling • : From Scheduling to Start Arriving • : The Queuing Delay

  4. Evaluation of Queuing Delay • ---- Size of Queuing Packets • ---- Queue Size • ---- Delay of Packet • Average Delay : . , , .

  5. Evaluation of Queuing Delay • Expectation of Packet Number: • Expectation of Delay Sum:

  6. With Same RTT for All ONUs • Conclusion 1: When the RTTs are the same for all ONUs, the order of transmission which minimizes the average packets delay is in descending order of queue sizes.

  7. With RTT Difference Greater than Guard Time • Conclusion 2: Assume that the RTT for is ,. If and are the two smallest of all RTTs and , then the optimal transmission order that minimizes the average packet delay must transmit of first.

  8. With RTT Difference Bound by Guard Time • Conclusion 3: If we have only two registered ONUs, with and . Then, when , we should transmit first. And when , we should transmit first.

  9. With RTT Difference Bound by Guard Time • Conclusion 4: If we have registered ONUs, with , and . The optimal transmission order transmits first such that , where for , and .

  10. Algorithm Explanation: We let , which is initiated as , denote the earliest arrival time of datas from to the OLT. We denote as the time instant up to which the upstreeam channel is occupied. In each round, as shown from line 5 to 25 in Algorithm 1, we choose an ONU, whose subscript is denoted as , among all un-scheduled ONUs based on the conclusions of section III, and let it transmit first. In line 21-25, we update the earliest arrival time of other unscheduled ONUs.

  11. Performance Evaluation • RTT is between 180us and 200us

  12. Performance Evaluation • RTT is between 50us and 200us

  13. Performance Evaluation • RTT is between 0us and 400us

  14. Conclusion • Two key factors of grant scheduling: RTTs & Grant Window Sizes • Smallest RTT first & Largest Grant Size first. • Our novel Integrated Grant Scheduling (IGS) algorithm integrates both heuristics and can provide lower average packet delay than any of these two heuristics.

  15. 谢 谢！

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