Strategy For Optimizing The Scheduling Of Upstream Resource In EPON With Remote Repeater Node

In recent years, there are many great progresses in the development of opticalnetworks. As one of the representative techologies in optical access networks, ethernetpassive optical network (EPON) obtained a rapid popularization and application. Thereare many researchs on innovation and application of EPON, the method adding remoterepeater node (RN) in the structure of EPON is one of them. This paper is mainly aboutthe Scheduling of upstream resource in EPON with RN, including the optimization ofscheduling and the algorithm for idle time eliminating and the scheme of systemsynchronous after idle time elimination.With the adding of RN, the performances of major traffics in EPON were promoted,but the mean delay of Inter traffic which have a large propotion in uplink was deteriorated.Besides, there is no special scheduling designed for RN, which limits the utilizing of RN'spotential function. In view of the above situations, this paper puts forward a strategynamed multiple-time division multiplex (M-TDM) for resource scheduling in EPON withRN. Based on the dynamatic bandwidth allocation algorithm and the cooperation of OLTand ONU and RN, this strategy allows multiple ONUs in EPON to send traffic at thesame time. Simulation results show that the strategy M-TDM can decrease mean delay ofInter traffic. Compared to original strategy, the performances of other traffics were alsopromoted.Idle time is one kind of time loss which exists in EPON upstream schedulingcommonly. The existing methods for eliminating idle time in EPON are not completelyfeasible M-TDM strategy with RN. So it needs to design a special algorithm that canadapt to M-TDM strategy and eliminate idle time effectively. After eliminating of idletime, the system of EPON with RN has to face another problem of ranging failure. Thisproblem is caused by Multi-Point Control Protocol (MPCP) frames, which have variablewaiting time in RN. Ranging failure will lead to the further failure of systemsynchronization, which is a serious network malfunction in time division multiplexsystem. In view of above problems, this paper proposed a special dynamic bandwidthallocation algorithm and a system synchronization scheme that can adapt to M-TDMstrategy. With the algorithm, ONUs are divided to two groups, and the idle time waselimited by the continuity between time slots of ONUs which belong to different zones. Under this system synchronization scheme, the waiting time of MPCP frame in RN wasfixed at a specific value. It guarantees the effectiveness of ranging and systemsynchronization. Simulation results show that the dynamic bandwidth allocationalgorithm and the system synchronization scheme proposed in this paper can meet thedesign requirements, they achieved expected effect.