Dynamic Bandwidth Allocation Algorithm For Ethernet Passive Optical Network Design And Simulation

Ethernet passive optical network (EPON) has been emerging as the best candidate for next-generation access network. It combines the passive optical network and Ethernet technologies, so it brings forth many beneficial features, such as large enough bandwidth, low cost of hardware, maintenance and upgrading, unique convenience to carry IP packets. One of EPON's key technologies determining the performance of EPON is statistically multiple access of the uplink, which is called dynamic bandwidth allocation (DBA) algorithm. IEEE published standard for EPON, the IEEE 802.3ah and introduced the "multi-point control protocol" to specify the media access control and management in EPON upstream transmission. The multi-point control protocol defines a master-slavery time division multiplexing scheme, which is the basis of DBA. Until now, world-wide researchers have proposed many good DBA algorithms. However, most of these algorithms do not ensure service level agreement of individual user and hence they are not fit for EPON deployment in China. Several DBA algorithms with different typicality are analyzed in detail in this paper and their advantages and shortcomings are explained.Based on the world-wide research work, the performance objectives of good DBA algorithm are concluded. Aiming at these objectives, for the first time in this field, design principles of DBA algorithm and corresponding methods to implement these principles are proposed in this paper. Resulting from analysis of all factors determining link utilization, three methods are suggested to boost uplink utilization. They are interleaved transmission to avoid idle stage of uplink during the DBA running, granting based on threshold-reporting to remove unused slot remainder and keeping the cycle length appropriate. Fairness in EPON can be defined as three types: inter-ONU fairness, inter-class fairness in differentiated services and inter-user fairness. With the possibility of several subscribers sharing one ONU, to ensure SLA compliance for each individual user is of significance in China. In order to support quality of service (QoS), DiffServ model should be adopted. With gated priority scheduling and properly selected cycle length, latency requirement of all classes of traffic can be satisfied. A feasible way to guarantee both inter-user fairness and inter-class fairness is hierarchically to allocate bandwidth to each class of each individual subscriber in proportion to subscriber's agreement bandwidth.Complying with aforementioned design principles and methods, a novel algorithm, named SOABR, is proposed in this paper. SOABR's outstanding performance is illustrated by comparison with IPACT, Chadi Assi's algorithm and HPFCT in theory. Also, simulation model of EPON is created with network simulation software OPNET Modeler. In the same simulation scenario, SOABR and two slightly modified SOABR, one excludes interleaved transmission and the other adopts full priority scheduling, are simulated. This experiment proves that the proposed design principles of DBA algorithm are effective. In another simulation experiment, SOABR, IPACT, Chadi Assi's algorithm and HPFCT are performed in the same scenario respectively. Simulation results show that SOABR has advantages in efficiency and inter-user fairness, which confirms theoretical conclusion.