Research On Dynamic Bandwidth Allocation Algorithm In EPONs

As the combination of Ethernet and Passive Optical Network technology, EPON has the same advantages of high bandwidth and passive components in PON. Meanwhile, there is no protocol conversion needed between EPON and the Ethernet device. EPON is universally viewed as the most appropriate solution to access network bandwidth bottleneck. How to allocate the bandwidth is a core problem in EPON, so more and more attention has been obtained.The issues of fairness in allocating the bandwidth are very important in the shared networks. Therefore, a novel improved dynamic bandwidth allocation (DBA) algorithm with the definition of fairness is proposed. Firstly, the priority of classification should be considered, and the bandwidth allocation is calculated in accordance with the strict priority of services. Secondly, the fixed bandwidth allocation strategies are applied to the high-priority service to ensure its performance. Then, the bandwidth will be allocated to the medium-priority and lower-priority services according to the size of the surplus bandwidth. If the surplus bandwidth can't meet the bandwidth request of medium priority, combined with the definition of fairness, the bandwidth request of light load will be satisfied firstly and the surplus bandwidth will be allocated by the weight between the high loads. The simulation results show that, compared with the basal algorithm, the novel algorithm improves the network performance.Cyclic Polling scheme is generally used in the dynamic bandwidth allocation, and there is an idle time when the up-stream channel is not utilized. In order to reduce the waste of time slot and improve the bandwidth utilization, the scheme of authorization in advance is proposed. Based on the existing scheme of authorization in advance, a novel predictive bandwidth allocation algorithm is proposed in this paper. First of all, the amount of high-priority traffic during the waiting time is predicted by using the high-order moving average model, in order to reduce the idle time slot and guarantee the performance of high priority. After that, the threshold is dynamically calculated by prediction, and some of the ONUs is authorized in advance. At last, the simulation results show that the algorithm can effectively improve the overall performance and reduce the packet loss rate.