Table of Contents
ISRN Communications and Networking
Volume 2011 (2011), Article ID 837453, 9 pages
http://dx.doi.org/10.5402/2011/837453
Research Article

A Novel Dynamic Bandwidth Allocation Mechanism for Star-Ring-Based EPON

1Department of Computer Science and Engineering, Yuan-Ze University, Chung-Li 32003, Taiwan
2Department of General Studies, Army Academy, Chung-Li 32092, Taiwan

Received 8 March 2011; Accepted 10 April 2011

Academic Editor: H. Shalaby

Copyright © 2011 I-Shyan Hwang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Ethernet Passive Optical Network (EPON) is proposed as a simple, cost-effective and scalable solution for bandwidth bottlenecks in access networks which can enhance the system performance because it transmits the aggregated high-speed traffic from hundreds of subscribers. Dynamic Bandwidth Allocation (DBA) mechanism has not yet been seriously considered for use in star-ring EPON architecture. In this paper, a distributed QoS-based dynamic bandwidth allocation (DQ-DBA) scheduling mechanism for the star-ring-based EPON architecture including optical line terminal (OLT), Sub-OLT and ONUs has been proposed to improve the system performance of traditional tree-based EPON architecture. In DQ-DBA, the highest-priority traffic of each ONU is directed to the OLT by the tree structure; moreover, the lower-priority traffic on each ONU is transmitted to the Sub-OLT by ring architecture. This approach can effectively resolve the idle period problem and reduce the overloading of OLT in conventional DBA mechanisms. Exhaustive simulation experiments are performed to compare the system performance between the tree and the star-ring architectures and validate the effectiveness of the proposed mechanism. Simulation results show that the proposed DQ-DBA mechanism in star-ring architecture can reduce packet delay and jitter for the high-priority traffic, thus ensuring the quality of service (QoS) regardless of subscriber numbers.