摘要 : 隨著能源節省在被動式光接取網路中受到重視，讓ONU(optical network unit)進入睡眠模式節省能源的方法已經變成重點。然而，在睡眠模式中是無法傳送或接收封包的，導致封包的延遲增加。所以決定ONU的睡眠時間，讓ONU進入睡眠模式節省能源的同時封包也不會違反封包延遲限制是一個挑戰。
Green Bandwidth Allocation (GBA) 研究分析模型且提出一個封閉型式的表示式來決定睡眠時間，這種方式將睡眠時間最大化且同時讓封包的平均延遲時間滿足延遲限制，然而網路中封包的抵達時間可能不會跟分析中假設的一樣。
本篇論文利用即時的資訊:REPROT訊息後的第一個和最後一個封包的抵達時間來決定可以同時讓封包滿足延遲限制和節省最多能源的睡眠時間，因為OLT(optical line terminal)缺少封包抵達時間的資訊，所以會擴展REPORT訊息額外攜帶上一個REPROT訊息後的第一個和最後一個封包的抵達時間給OLT，此外，因為OLT需要對即時的封包抵達時間做回應，所以使用on-line的separated polling。實驗結果顯示我們封包違反延遲限制的比例比GBA還低同時能源節省與GBA的差距不到1%。
*作者 **指導教授

Abstract– Concerns about energy efficiency in the Ethernet passive optical network (EPON) are growing. In response, enabling optical network units (ONUs) to enter low-power sleep mode has become a focus in reducing energy consumption. However, in sleep mode, packets can not be transmitted, and so packet delays increase. Accordingly, the sleep time decision of when the ONU can enter sleep mode to conserve energy, yet not violate the delay constraints, becomes a challenge.
Green Bandwidth Allocation (GBA) was used to study the analytical model and propose a closed-form expression to determine the sleep time. In this manner, sleep time can be maximized for energy savings while simultaneously ensuring the average packet delay can satisfy the delay constraint. However, the packet arrival in the network may not be the same as the analytical assumption.
In this thesis, we start from determining the sleep time from a real-time information: first packet arrival time after REPORT message to keep packets satisfying delay constraint and meanwhile conserve energy as great as possible. Nevertheless, the sleep time decided by first packet arrival time causes a frequent transition overhead which wasted a lot of energy. Hence the last packet arrival time after REPORT message and a ratio parameter is added to enlarge sleep time so as to decrease transition overhead frequency. Since the OLT lacks packet arrival time information, the extension to the REPORT message carrying additional first and last packet arrival times after the last REPORT is sent to the OLT. Moreover, since the OLT needs to respond to the real-time arrival information, an on-line separated polling scheme and scheduling is presented. Simulation results showed that the percentage of packets violating the delay constraint can be lower than the GBA; however, the energy saving difference is no more than 1%.

REFERENCES
[1]. K. J. Christensen, C. Gunaratne, B. Nordman, and A. D. George, “The next frontier for communications networks: Power management,” Computer Communications, vol. 27, no. 18, pp. 1758‒1770, Dec. 2004.
[2]. N. Ansari and J. Zhang, “Media Access Control and Resource Allocation for Next Generation Passive Optical Networks,” Springer, 2013.
[3]. R. Bolla, R. Bruschi, F. Davoli and F. Cucchietti, “Energy efficiency in the Future Internet: A survey of existing approaches and trends in energy-aware fixed network infrastructures,” IEEE Communications Surveys and Tutorials, vol. 13, pp. 223-244, May 2011.
[4]. D. Jiang, Z. Xu, Z. Chen, Y. Han and H. Xu, “Joint time-frequency sparse estimation of large-scale network traffic,” Computer Networks, vol. 55, pp. 3533-3547, Jun. 2011.
[5]. D. Jiang, G. Hu, “GARCH model-based large-scale IP traffic matrix estimation,” IEEE Communications Letters, vol. 13, pp. 52-54, Jan. 2009.
[6]. J. Jung, W. Yang, Y. Kim, “A bandwidth allocation algorithm for improving QoS in EPON with sleep mode,” in Information Networking (ICOIN) 2012, pp. 324-328, Feb. 2012.
[7]. J. Baliga, R. Ayre, K. Hinton, W. V. Sorin, and R. S. Tucker, “Energy Consumption in Optical IP Networks,” IEEE/OSA Journal of Lightwave Technology, vol. 27, no. 13, pp. 2391‒2403, Jul. 2009.
[8]. Y. Zhang, P. Chowdhury, M. Tornatore, and B. Mukherjee, “Energy efficiency in telecom optical networks,” Communications Surveys & Tutorials, IEEE, vol. 12, no. 4, pp. 441‒458, Jul. 2010.
[9]. J. Baliga et al., “Energy consumption in wired and wireless access networks,” Communications Magazine, IEEE, vol. 49, no. 6, pp. 70‒77, Jun. 2011
[10]. Ethernet in the First Mile Task Force, IEEE 802.3ah, Sep. 2004
[11]. J.-I. Kani, F. Bourgart, A. Cui, A. Rafel, and S. Rodrigues, “Next-generation PON—Part 1: Technology roadmap and general requirements,” IEEE Communication Magazine, vol. 47, no. 11, pp. 43–49, Nov. 2009.
[12]. J. Mandin, “EPON powersaving via sleep mode,” IEEE P802.3av 10GEPON Task Force Meeting, www.ieee802.org/3/av/public/2008_09/3av_0809_mandin_4.pdf, Sep. 2008.
[13]. S. Wong, L. Valcarenghi, S. Yen, D. Campelo, S. Yamashita, and L. Kazovsky, “Sleep mode for energy saving PONs: Advantages and drawbacks,” IEEE GLOBECOM Workshops, pp. 1-6. Nov. 2009.
[14]. S. Wong, S. Yen, P. Afshar, S. Yamashita, and L. Kazovsky, “Demonstration of Energy Conserving TDM-PON with Sleep Mode ONU Using Fast Clock Recovery Circuit,” Optical Fiber Communication, pp. 1-3, Mar. 2010.
[15]. ITU-T, “GPON Power Conservation,” ITU-T series G Supplement 45.
[16]. B. Skubic and D. Hood, “Evaluation of ONU power saving modes for gigabit-capable passive optical networks,” IEEE Network, vol. 25, no. 2, pp. 20–24, Mar.–Apr. 2011.
[17]. “IEEE 802.3az Energy Efficient Ethernet Task Force,” 2010 [Online]. Available: http://www.ieee802.org/3/az/index.html
[18]. Y. Yan, S. Wong, L. Valcarenghi, S. Yen, D. Campelo, S. Yamashita, L. Kazovsky, L. Dittmann,”Energy Management Mechanism for Ethernet Passive Optical Networks (EPONs),” in Proceedings of 2010 IEEE International Conference on Communications, pp. 1-5, May 2010.
[19]. Y. Yan and L. Dittmann, “Energy Efficiency in Ethernet Passive Optical Networks (EPONs): Protocol Design and Performance Evaluation,” Journal of Communications, vol. 6, no. 3, pp. 249‒261, May 2011.
[20]. J. Zhang and N. Ansari, “Toward Energy-Efficient 1G EPON and 10G-EPON with Sleep-Aware MAC Control and Scheduling,” IEEE Communications Magazine, vol. 49, no. 2, pp. S33-S38, Feb. 2011.
[21]. A. R. Dhaini, P. H. Ho, and G. Shen, “Toward Green Next-Generation Passive Optical Networks,” IEEE Communications Magazine, vol. 49, no. 11, pp. 94‒101, Nov. 2011.
[22]. A. R. Dhaini, P. H. Ho, G. Shen, B. Shihada, “Energy Efficiency in TDMA-Based Next-Generation Passive Optical Access Networks,” IEEE/ACM Transactions on Networking, vol. 22, no. 3, pp. 850‒863, Jun. 2014.
[23]. A. R. Dhaini, P. H. Ho, and G. Shen, “Energy Efficiency in Ethernet Passive Optical Networks: For How Long Can ONU Sleep?” Univ. of Waterloo tech. rep., Mar. 2011.
[24]. X. Bai, A. Shami, and Y. Ye, “Delay analysis of Ethernet passive optical networks with quasi-leaved polling and gated service scheme,” Access Networks & Workshops, pp. 1‒8, Aug. 2007
[25]. A. Varga, “The OMNeT++ discrete event simulation system,“ Proceedings of the European Simulation Multiconference, pp. 319‒324, Jun. 2001.
[26]. G. Kramer, B. Mukherjee, S. Dixit, Y. Ye, and R. Hirth, “Supporting differentiated classes of service in Ethernet passive optical networks,” Journal of Optical Networking, vol. 1, no. 8, pp. 280‒298, Aug. 2002.
[27]. W. Leland, M. Taqqu, W. Willinger, and D. Wilson, “On the self-similar nature of Ethernet traffic (extended version),”IEEE/ACM Transactions on Networking,vol. 2, no. 1, pp. 1-15, Feb. 1994.