Fitting Scheduling Timing–Elastic Weighted Granting (FST–EWG): An EPON DBA Algorithm

Abstract

Online scheduling algorithms incur no idle time problem but with less bandwidth efficiency, while offline scheduling algorithms focus on bandwidth efficiency but with idle time overhead. Although a just-in-time (JIT) scheduling algorithm for multi-channel Ethernet passive optical networks (EPONs) has been proposed to increase the bandwidth efficiency without the idle time overhead, its applicability to single-channel EPONs is problematic. A new algorithm called fitting scheduling timing–elastic weighted granting (FST–EWG) is proposed and is suitable for single-channel EPONs. First, the FST determines the fitting timing for performing the dynamic bandwidth allocation scheduling algorithm in an attempt to consider as many optical network unit (ONU) demands as possible and to avoid the unnecessary idle time as much as possible. Then the EWG can efficiently re-allocate the excess bandwidth of light-load ONUs to all heavy-load ONUs. The computation complexity of the proposed FST–EWG is linear and is denoted as O(N), where N is the number of ONUs. Simulation results show that FST–EWG efficiently allocates bandwidth compared to previously proposed algorithms in terms of average packet delay and packet dropping probability, especially for higher load. In addition, by adding the non-strict priority intra-ONU scheduling, FST–EWG also outperforms the previously proposed DBAM method in terms of EF average delay and EF delay variation.