Study Of Unstream Access Technology And Dynamic Bandwidth Allocation Algorithm In Ethernet PON

With the dramatical increasing of the network service, the network's transmission ability had been improved a lot in recent years. At the same time, both the backbone network and the high speed LAN were upgraded, however, the access network that connects backbone network and LAN is becoming the bottleneck of the development of information superhighway . Although current broadband access methods, such as x DSL, Cable Modem and LMDS are widely used, can satisfy the requirement in some ways so far, they don't have the ability to provide enough bandwidth to meet the increasing requirement such as IPTV, VOD, Video meeting, VOIP and so on. Fiber To The House (FTTH ) is the destination of the future's network, and Ethernet Passive Optical Network (EPON) is one of the ideal technologies to realize that, which represents the latest development trend of the access network. Moreover, FTTH is the hottest researches area of current board access network.Allocation arithmetic of the uplink bandwidth have become the hot techniques in the EPON system due to the uplink's ONU sharing bandwidth topology structure. This dissertation introduces the system structure and related key technologies of EPON system;several current allocation algorithms of the bandwidth are analyzed also. After compares the merits and weaknesses of these algorithms, the paper introduces a improved algorithms of allocation algorithms of the uplink bandwidth. This presented algorithm is based on services classification and bandwidth partition. The key points of this algorithms are to classify the upstream services into several priorities and then according to the priority of the ONU of the bandwidth, the uplink bandwidth assigned to a registered ONU is partitioned into high priority bandwidth, middle priority bandwidth and low priority bandwidth, accordingly. The high priority bandwidth is applied for the TDM services with constant bit rate and morestrict requirements on delay and jitterf and is granted regularly to satisfy the periodical characteristic of TDM service. While the middle priority bandwidth is applied for the paroxysmal and high-speed Viode service, the low priority bandwidth is applied for data service, they are granted owing to the allocation schemes of the improved algorithm.In the end, the simulation model on OPNET is set up according to the EPON system. By analyzing the results of the simulation, it showed that the EPON model of the new algorithm is better than that with other traditional algorithms based on the throughput, delay and fairness.