Research Of Uplink Bandwidth Dynamic Allocation Algorithm In EPON

EPON combines the mature Ethernet technology with the passive optical network, possesses high bandwidth, low-cost, easy expansion, good compatibility features, etc, and is the one of the best next generation access network which have important technical means to realize multi-service access, all-optical networks. EPON topology is a typical tree structure, a number of ONU and one OLT been linked by ODN and using TDMA mode to share upstream bandwidth, therefore it is necessayr to adopt bandwidth allocation algorithm to coordinate ONU uplink data transmission. The goal of algorithm is not only to avoid uplink data conflict, but also ensures the uplink channel in a fair and efficient use and all services Qos. Dynamic bandwidth allocation algorithm is one of hot research of EPON, and is also the focus of this paper.The paper analyzes MPCP protocol and the realization process of DBA algorithm firstly, then studies the classical dynamic bandwidth allocation algorithm of EPON, at last summarizes up the problems of classical algorithms and proposes algorithm design principles.Facing to the problem of idle time of EBA and all fixed cycle algorithm, the paper adopts granting mechanism in advance and brings forward N-EBA algorithm which combines EBA algorithm and granting mechanism in advance. As far as the scheduling mode between the ONUs, N-EBA algorithm grants the appropriate ONU in advance according to priority of the ONUs,and transports data effectively and fully using bandwidth which idle time waste. As far as ONU internal queue schduling mode, N-EBA algorithm takes effective internal ONU queue scheduling algorithm which take low-priority traffic into account, and overcome the shorting of strict priority schduling which low-priority traffic can't been transported under heavy load system. The algorithm not only ensures high-priority traffic QoS, but also reduces low-priority packets delay effectively. The paper also raises the REPORT and GATE frame format based on MPCP protocol to meet N-EBA algorithm function.The paper implements network modeling, node modeling and process modeling in OPNET platform according to EPON reference model and the workflow of ONU and OLT. N-EBA algorithm simulate along with EBA algoritm under the same parameter, and the simulation showes that the algorithm possesses the higher bandwidth utilization and fine average packets delay, excellent delay jitter and ensures different traffic QoS.