Dynamic Bandwidth Allocation Algorithms In Ethernet Passive Optical Networks

Ethernet Passive Optical Networks (EPONs), which converge the simplicity and universality of Ethernet facilities and large-capacity, steady-performance and low-cost of PONs, has emerged as one of the most promising solution for broadband-access-network bottleneck problem. Even though the standardization of EPON has been accomplished, there still have lots of problems which are needed to be solved due to the open characteristic of IEEE802.3ah protocol. In this paper, we investigated the problems of dynamic bandwidth allocation in EPONs, the upgrading of EPON and bandwidth allocation in WDM EPONs, and proposed three new algorithms, which are evaluated by extensive simulations.The architecture for upstream direction in EPON is MP2P, where all ONU share the same upstream wavelength channel through TDM style. Therefore, an appropriate bandwidth (timeslot) allocation scheme is needed to regulate transmission of each ONU. Typical fixed maximum cycle time schemes have idle time in every grant cycle, which degrades the network porformance. This paper proposed an idle time minimized (ITM) dynamic bandwidth allocation algorithm to solve this problem. ITM-1 and ITM-2 can reduce and even delete this idle time by granting a group of ONUs to send report messages earlier. The simulation results show that, ITM clearly improves channel efficiency and enhances the whole network performance compared with previous algorithms.Since the rapid development of broadband application techniques and the increasing of bandwidth requirements and amount of users, the existing Time Division Multiplexing (TDM) EPON can not fully satisfied users' requirements in the future. For this reason, an incremental migration is needed from TDM EPON to WDM EPON. Due to the load unbalance between different wavelength channels derived by existing DBA schemes, which will waste bandwidth, this paper proposed a load-balanced dynamic bandwidth allocation (LB-DBA) algorithm. The simulation results show that, LB-DBA algorithm significantly improved system performances through balancing different wavelength channel load.As TDM EPON is being on-demanded upgrading to WDM EPON, the number of wavelengths supported by varied ONUs will be different. Existing WDM EPON dynamic bandwidth allocation algorithms will decrease the network performance. As a result, we proposed a new dynamic bandwidth allocation algorithm for upgrading WDM EPONs (DBA-U). The simulation results show that, not only does DBA-U algorithm the allocations of bandwidth and wavelengths more reasonable in upgrading WDM EPONs, but also reduce the update cost for some situation.