Dynamic Resource Scheduling Algorithms In Next-generation Passive Optical Networks

Compared with the Ethernet Passive Optical Network(EPON),the Next Generation Passive Optical Network(NG-PON)can provide higher data rate and more low-cost broadband access service for more users.And it has got widespread attention from the industry and the academic community.With the growing demand for bandwidth,the data traffic carried by a NG-PON is also explosively growing.Consequently,efficient dynamic resource scheduling algorithm is the key to ensure the network performance,and it has currently become one of the hot problems to be solved urgently in NG-PONs.First,the background of NG-PONs and the network structure and recent research progress of Long Reach Passive Optical Networks(LR-PON)and Wavelength-Agile PONs(WA-PON)are presented,and traditional dynamic resource allocation algorithms for EPONs and LR-PONs as well as WA-PONs are analyzed in this paper.Secondly,aiming at the load distributed nonuniformly in an LR-PON with considerable propagation delay and bursty traffic,a Hybrid-Scheduling Adaptive Multi-Thread Polling algorithm(HS-AMTP)has been proposed.The HS-AMTP which combines the advantages of online scheduling scheme and offline scheduling scheme,can adjust the number of polling dynamically according to the bandwidth requirements from Optical Network Units(ONU)through gate-driven polling.Therefore,it is helpful to improve the performance of average packet delay and upstream channel utilization.Thirdly,a Void-Filling Based Partial Multi-Thread Polling algorithm(VF-PMTP)has been proposed for an LR-PON with heterogeneous propagation delays.The VF-PMTP algorithm works on a combined online and offline scheduling scheme for the coexisting long-distance and short-distance ONUs.Besides,VF-PMTP algorithm can adjust the grant times for the long-distance ONUs depending on whether the channel is idle while applying online single-thread polling algorithm to the short-distance ONUs so as to decrease overall networks average packet delay and to improve upstream channel utilization.And then,focusing on a WA-PON with bursty traffic and limited wavelength resource,based on the existing Water-Filling(WF)algorithm,an improved Delay Fairness-aware Dynamic Wavelength and Bandwidth Allocation(DF-DWBA)algorithm has been proposed,which can adjust the number of upstream wavelength channels assigned to a given ONU dynamically according to the bandwidth request of the ONU and the effect on the delays of other ONUs.Therfore,it is beneficial to improve the the performance of average packed delay,upstream channel utilization and delay fairness index.Finally,LR-PONs and WA-PONs are modeled by OPNET,and the performance of the proposed algorithms are compared with several existing algorithms in the literature by extensive simulations.The simultion results verified the effectiveness of the proposed algorithms.