The advantages of Ethernet passive optical network (EPON) are setting it to be a natural ubiquitous solution for the access network. In the upstream direction of EPON, the directional property of the splitter requires that the traffic flow be mitigated to avoid collision. A dynamic bandwidth allocation (DBA) scheme is desirable in optimizing the bandwidth usage further. In this paper, a global priority DBA mechanism is discussed. The mechanism aims to reduce the overall delay while enhancing the throughput and fairness. This study was conducted using MATLAB where it was compared to two other algorithms in the literature. The results show that the delay is reduced up to 59% and the throughput and fairness index are improved up to 10% and 6%, respectively. 1. Introduction One of the most attractive solutions to the last mile bandwidth bottleneck in communication systems is Ethernet passive optical network (EPON). It gains its popularity due to the large coverage area, the reduction in energy usage as compared to copper, the reduction in fiber deployment, and lower cost of maintenance [1]. In EPON, collision may occur in the upstream transmission when multiple optical network units (ONUs) transmit data to the optical line terminal (OLT) simultaneously. It occurs because the data from multiple ONUs need to share the same fiber from the splitter to the OLT. A current method of avoiding collision is by using dynamic bandwidth allocation (DBA) algorithm. Up to date, a number of DBA algorithms have been proposed in the literature [2–12]. In general, we can divide the algorithms into two parts: DBAs that use one logical link identifier (LLID) per ONU and DBAs that use multiple LLIDs per ONU. One LLID per ONU means that an LLID is allocated to the entire ONU. It creates a hierarchical scheduling structure in which the OLT assigns the bandwidth to the ONUs and the ONUs will further subdivide the bandwidth to multiple queues inside the ONU. On the other hand, multiple LLIDs per ONU mean that an LLID is allocated to each queue in every ONU. Luo and Ansari [2] propose DBA with multiple services algorithm that combines limited scheduling in inter-ONU allocation with nonstrict priority scheduling in intra-ONU allocation. Excessive bandwidth is also combined with a nonstrict priority scheduling in [3]. However, the shortcoming of this method is increased queuing delay because all packets would have to wait a full cycle between report and transmission. In order to overcome the problem in nonstrict priority scheduling, strict priority scheduling is used. It allows newly
References
[1]
I. S. Hwang, J. Y. Lee, and Z. D. Shyu, “A novel dynamic bandwidth allocation mechanism for star-ring-based EPON,” ISRN Communications and Networking, vol. 2011, Article ID 837453, 9 pages, 2011.
[2]
Y. Luo and N. Ansari, “Bandwidth allocation for multiservice access on EPONs,” IEEE Communications Magazine, vol. 43, no. 2, pp. S16–S21, 2005.
[3]
C. Sue and W. Sung, “Fitting scheduling timing-elastic weighted granting (FST-EWG): an EPON DBA algorithm,” Journal of Optical Communications and Networking, vol. 4, no. 6, pp. 468–479, 2012.
[4]
D. Nikolova, B. Van Houdt, and C. Blondia, “Dynamic bandwidth allocation algorithms for ethernet passive optical networks with threshold reporting,” Telecommunication Systems, vol. 28, no. 1, pp. 31–52, 2005.
[5]
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. 9, pp. 280–298, 2002.
[6]
H. Lee, W. Yoon, T. Lee, H. Choo, and M. Chung, “Two-Phase Cycle DBA (TCDBA) for differentiated services on EPON,” IEICE Transactions on Communications, vol. 92, no. 9, pp. 2823–2837, 2009.
[7]
M. V. Dolama and A. G. Rahbar, “Modified smallest available report first: new dynamic bandwidth allocation schemes in QoS-capable EPONs,” Optical Fiber Technology, vol. 17, no. 1, pp. 7–16, 2011.
[8]
N. Merayo, R. J. Durán, P. Fernández, R. M. Lorenzo, I. De Miguel, and E. J. Abril, “EPON bandwidth allocation algorithm based on automatic weight adaptation to provide client and service differentiation,” Photonic Network Communications, vol. 17, no. 2, pp. 119–128, 2009.
[9]
S. I. Choi and J. Park, “SLA-aware dynamic bandwidth allocation for QoS in EPONs,” Journal of Optical Communications and Networking, vol. 2, no. 9, Article ID 5560808, pp. 773–781, 2010.
[10]
A. Shami, X. Bai, C. M. Assi, and N. Ghani, “Jitter performance in Ethernet passive optical networks,” Journal of Lightwave Technology, vol. 23, no. 4, pp. 1745–1753, 2005.
[11]
H. Naser and H. T. Mouftah, “A joint-ONU interval-based dynamic scheduling algorithm for ethernet passive optical networks,” IEEE/ACM Transactions on Networking, vol. 14, no. 4, pp. 889–899, 2006.
[12]
F. D. M. Pereira, N. L. S. da Fonseca, and D. S. Arantes, “A fair scheduling discipline for Ethernet passive optical networks,” Computer Networks, vol. 53, no. 11, pp. 1859–1878, 2009.
[13]
X. Bai, A. Shami, and C. Assi, “On the fairness of dynamic bandwidth allocation schemes in Ethernet passive optical networks,” Computer Communications, vol. 29, no. 11, pp. 2123–2135, 2006.
[14]
V. Paxson and S. Floyd, “Wide area traffic: the failure of Poisson modeling,” IEEE/ACM Transactions on Networking, vol. 3, no. 3, pp. 226–244, 1995.
[15]
G. Kramer, B. Mukherjee, and G. Pesavento, “Interleaved polling with adaptive cycle time (IPACT): a dynamic bandwidth distribution scheme in an optical access network,” Photonic Network Communications, vol. 4, no. 1, pp. 89–107, 2002.
[16]
D. Sala and A. Gummalla, “PON functional requirements: services and performance,” presented at the IEEE 802.3ah meeting in Portland, Ore, July 2001, http://www.ieee802.org/3/efm/public/jul01/presentations/sala_1_0701.pdf.
