Qos-based Epon Key Technology Research

In recent years, with the substantial change of the telecommunication backbone, the access network has become a bottle neck between high-capacity local network and the backbone network. The Passive Optical Network (PON) which has many advantages, such as broad bandwidth, huge capability, and powerful interference rejection suits very much as the transmission access network medium for high-speed broadband network. However, PON is a kind of pure medium network and It must work with the data link layer protocol. Due to popularization of Internet and the IP service, the Ethernet which was developed for the load bearing IP service has become the standard which generally accepted. Thinking of the actuality of the IP network and the ability of PON transport, EPON(Ethernet Passive optical network)is considered to be one of the ideal solutions to implement future broadband access network, even be the final technology to implement FTTH. At the same time, the gradual integration of the data, voice and video networks has brought new requirements to the transmission network called low delay, and little jitter so it is very important to reduce the packet delay and packet loss rate to raise the service quality of EPON. This paper analyzed the present situation of access network as well as the EPON superiority, introduced the EPON principle as well as several key technologies of the datalink layer and mainly focused on raising the service quality of EPON. The paper's argument and achievement mainly includes the following several aspects:Firstly, Researched on the discovery and register technology of ONU (Optical Network Unit) ,compared two solution of register conflict. The paper proposed a new solution based on register cycle and carried on an analysis to the register cycle appropriate selection to improve the bandwidth utilization and the service quality.Secondly, Elaborated the architecture and transmission principle of EPON system, Took an analysis on the Multiple Access scheme in details and a deep research on the principle of TDMA.Thirdly, Conducted the ranging research technology in the TDMA scheme. Proposed the TimeStamp ranging scheme and elaborated its principle as well as the initial ranging and dynamic ranging process.Finally, the paper conducted in-depth research to the MPCP protocol and the dynamic bandwidth allocation(DBA). After analyzing the disadvantages of the current DBA algorithms, this thesis presents an InterServ-supported algorithm based on prediction rectification that supports bandwidth pre-allocation. The rectification scheme is introduced to improve the bandwidth utilization. Once the bandwidth pre-allocated to high priority services is surplus, the rectification scheme will start to work from the next circle. Computer simulation results showed that ISDP algorithm could meet the delay demands of high priority services and control the delay abnormity of low priority services simultaneously.