Research On Prediction And Correction-based Uplink Dynamic Bandwidth Allocation Algorithm In EPON

Ethernet passive optical network (EPON) based on the advantages of itsbandwidth-rich, low cost, easiness to expand and maintain, as the best carrier of IP, hasbecome the best way to solve the problem of the access to network "last mile". In orderto make multiple ONUs share upstream bandwidth, we adopt the method of the TDM(Time Division Multiple) in the uplink direction of EPON. Dynamic bandwidthallocation algorithm (DBA) arbitrates the upstream bandwidth, which not only canavoid collision from the upstream data transmission, but also can utilize the upstreamchannel fairly, orderly and efficiently.This paper makes a special emphasis on the dynamic bandwidth allocationalgorithm for EPON system，which is based on the research of the system architectureand key technology in EPONFirstly, we do a depth analysis of the mechanism with the up/down data transfer,multi-point control protocol (MPCP) and the key technologies of EPON, andemphatically study on the multi-service-based and forecast-based DBA algorithm. Thenbased on full analysis of the predicted mechanism, we present a kind of the mechanismof predicted–correction from which the correction factor can be used for amendingthe predicted value, in order to make it closer to the true value.Secondly, facing to the deficiencies in the existing DBA algorithm, this paper forward a dynamic bandwidth allocation algorithm with Correction-based MultipleTraffic Prediction mechanism (CMP-DBA) which combined with a multi-servicemechanism and prediction-correction mechanism. To begin with, the traffic fromdifferent ONU is divided three categories of EF(expedited forwarding), AF(AssuredForwardin) and BE(Best Effort) in terms of the priority level of the traffic, and then itmakes the traffic of different priority services predicted, and corrects predicted valueaccording to the Gaussian distribution characteristic of the prediction error. So that thepre-assigned bandwidth is much closer to the real traffic, thereby improving thereal-time feature of bandwidth allocation.Finally, this paper builds a simulation model of the three-tier communicationEPON system on the OPNET simulation platform, which is as follows: networkmodeling, node modeling and process modeling. Under the same parameters, theCMP-DBA algorithm will be compared with multi-service-based algorithm, at the sametime we will also make a comparison of this algorithm of performance before and afteradopting the correction mechanism.The simulation shows that the CMP-DBA algorithm can not only meet therequirements of the high-priority business delay, but also can control the abnormality ofthe low-priority business delay. In addition, with rectification scheme, it obviouslyimproves the bandwidth utilization, and assures the characteristics of different businessQoS, smaller delay jitter and so on.