在過去的幾年中，分時多工被動式光接取網路被認為是一種有經濟效益的頻寬接取技術。隨著能源問題越來越被重視，能源的使用效率逐漸成為一個重要的問題。在被動光接取網路中，其中一種節能方式是讓ONU(Optical Network Unit)關閉發送器與接收器進入耗能較低的睡眠模式，在這段期間，ONU無法收發封包，會導致封包延遲時間的增加，因此封包的延遲時間與功率消耗之間存在著難以取捨的權衡關係。Green bandwidth allocation(GBA)的作者提出利用批次傳輸的特性來減少ONU因為頻繁的模式轉換所產生的能源消耗，並且根據封包的延遲時間限制決定各個ONU的睡眠時間，讓ONU可以最大化睡眠時間且不違反封包的最大延遲時間限制，來得到最佳的省電效果。
但若每個ONU最大延遲時間限制不同，算出來的睡眠時間也不同，採用GBA提出的機制，會造成ONU與ONU之間的睡眠時間互相影響，而造成最大延遲時間限制較小的ONU封包違反其延遲時間限制。因此本文提出Group By Remaining Sleep time(GBRS)，透過檢查ONU剩餘的睡眠時間，依照睡眠時間的長短，將ONU分配到不同的群，以避免ONU封包違反各自的延遲時間限制。最後，我們將ONU設定不同的最大延遲時間限制來量測效能，並測試多種組合，模擬結果顯示，GBRS的分群機制可讓ONU在不同測試組合中，維持ONU封包各自的延遲時間限制。

Time-division-multiplexing passive optical network (PON) has been considered in the past few years as a cost-effective broadband access technology. With the ever-increasing power saving concern, energy efficiency has been an important problem in PONs’ operations. To save energy in PONs, one of the methods is to allow the optical network unit (ONU) to go into sleep mode. In this mode, ONU can’t transmit and receive frames, so the frame delay may increase. Therefore, there is a tradeoff between frame delay and power consumption. It’s hard to give consideration to both frame delay and power consumption. The authors of Green bandwidth allocation (GBA) proposed a framework which uses the batch-mode transmission feature to minimize the frequency of ONU in on-off transitions. The optimal sleep time of each ONU is determined in every cycle without violating the maximum delay constraint.
However, if each ONU has different maximum delay constraint, using the maximum delay constraint to decide the sleep time may cause some packets of ONU to violate theirs delay constraint. Accordingly, we proposed a framework called “Group By Remaining Sleep time” that inspects the remaining sleep time and groups ONUs by the sleep length every cycle to avoid violating each ONU’s frame delay constraint. Finally, we set up ONUs with different delay constraint to evaluate the performance of GBRS. The simulation result shows that the grouping method of GBRS keep ONUs not impair their delay constraint in different test cases.

[1] Ethernet in the First Mile Task Force, IEEE 802.3ah, Sep. 2004.
[2] Gigabit-capable Passive Optical Networks (G-PON): Transmission convergence later specification, ITU-T Rec. G.984.3., Mar. 2003.
[3] One-Way Transmission Time, ITU-T Rec. G.114., June 2005.
[4] R. Kooij, K.Ahmed, and K. Brunnström, “Perceived quality of channel zapping,” in Proceedings of the Fifth IASTED International Conference Communications Systems and Networks, pp. 155-158, Aug. 2006.
[5] Z. Begic, M. Bolic, H. Bajric, “Effect of multicast on IPTV channel change performance,” 50th International Symposium ELMAR, vol. 1, pp. 151-155, Sep. 2008.
[6] Media Access Control (MAC) Bridges, IEEE Standard 802.1D, June 1998.
[7] A. Dhaini, C. Assi, M. Maier, A. Shami, “Per-Stream QoS and admission control in Ethernet passive optical networks (EPONs),” IEEE/OSA Journal of Lightwave Technology, vol. 25, no. 7, pp. 1659-1669, Jul. 2007.
[8] W. Tang, C. Huang, C. Chang, F. Ren, “QoS-promoted dynamic bandwidth allocation for ethernet passive optical networks,” in Proceedings of Third International Conference on Communications and Networking in China(CHINACOM), pp. 252-256, Aug. 2008.
[9] GPON Power Conservation, ITU-T series G Supplement 45.
[10] 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.
[11] A. R. Dhaini, P. H. Ho, G. Shen, “Energy efficiency in Ethernet passive optical networks: for how long can ONU sleep?” Univ. of Waterloo tech. rep., Mar. 2011.
[12] 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, June 2014.
[13] S. Wong, L. Valcarenghi, S. Yen, D. Campelo, S. Tamashita, L. Kazovsky, “Sleep mode for energy saving PONs: advantages and drawbacks,”2009 IEEE GLOBECOM Workshops, pp. 1-6. Nov. 2009.
[14] J. Mandin, “EPON power saving via sleep mode,” IEEE 802.3za Meeting, Sep. 2008.
[15] S. S. W. Lee, and A. Chen, “Design and analysis of a novel energy efficient Ethernet passive optical network,” in Proceedings of ICN, pp. 6-9, Apr. 2010.
[16] Y. Yan, S. W. Wong, L. Valcarenghi, “Energy management mechanism for Ethernet passive optical networks (EPONs),” in Proceedings of 2010 IEEE International Conference on Communications (ICC), pp. 1-5, May 2010.
[17] Y. Yan, 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.
[18] 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. 33-38, Feb. 2011.
[19] L. Shi, B. Mukherjee, S. S. Lee, “Energy-efficient PON with sleep-mode ONU: progress, challenges, and solutions,” IEEE Network, vol.26, no.2, pp.36-41, Apr. 2012.
[20] L. Shi, B. Mukherjee, S. S. Lee, “An SLA-based energy-efficient scheduling scheme for EPON with sleep-mode ONU,” in Proceedings of Optical Fiber Communication Conference and Exposition (OFC/NFOEC), pp. 1-3, Mar. 2011.
[21] A. Dixit, B. Lannoo, D. Colle, M. Pickavet, P. Demeester, “Energy efficient dynamic bandwidth allocation for Ethernet passive optical networks,” 2012 IEEE International Conference on Advanced Networks and Telecommuncations Systems (ANTS), pp.16-19, Dec. 2012.
[22] A. Varga, “The OMNeT++ discrete event simulation system,” in Proceedings of the European Simulation Multiconference (ESM), pp. 319-324, June 2001.