Energy Efficiency in Ethernet Passive Optical Networks (EPONs): Protocol Design and Performance Evaluation

As concerns about energy consumption grow, the power consumption of the EPON becomes a matter of increasing importance. In respect of energy efficiency, the current standard has no management protocols aiming to reduce power consumption in EPONs. In this paper, we propose an Energy Management Mechanism (EMM) for downlink EPON systems. The proposed mechanism is designed to enhance the standardized control scheme in EPON with the objective to increase energy efficiency while satisfying diverse QoS requirements. The main idea is to put an Optical Network Unit (ONU) into the sleep mode and determine a suitable wakeup time scheduler at the Optical Line Terminal (OLT). A generic EPON system is considered, which is composed of an OLT and several ONUs that are EMM enabled. An energy consumption optimization problem aimed at saving energy is proposed and two heuristic sleep mode scheduling policies are addressed to solve it. The scheduling algorithms are tightly coupled with the upstream bandwidth allocation and downstream transmission scheduling together through an integrated approach in which awake time in ONUs is minimized. There is a trade-off decision between maximizing the power saving and guaranteeing the network performance at the same time. Simulation results show that an EMM-based EPON with well designed scheduling disciplines is essential to achieving significant energy saving while meeting the delay constraint.