The QoS provisioning tri-mode energy saving mechanism for EPON networks

The Ethernet passive optical network provides broadband Internet access but also consumes a lot of energy. Energy saving mechanisms using the dual-mode-Active and Sleep modes-design for optical network unit (ONU) in EPON still suffer unnecessary energy consumption, especially in asymmetric data flow such as video streaming downloading service. The Doze mode is particularly suitable for handling the asymmetric data flow since it allows the ONU's transmitter to turn off while turning on its receiver to receive data from optical line termination (OLT). However, adding Doze mode into original dual-mode design incur a greater challenge for OLT to identify the current status of the ONU since the ONU cannot transmit any upstream message to OLT at either Doze or Sleep mode. In this paper, we propose a new QoS provisioning tri-mode energy saving scheme, by integrating the Doze mode into original dual-mode design, to allow the ONU to switch to one of the energy saving modes whenever no upstream traffic exists. A high-priority upstream packet, arriving at ONU of energy saving modes, is able to trigger the ONU back to Active mode for QoS provisioning purpose. Performance evaluation via simulation has demonstrated the effectiveness of such mechanism in various asymmetric data flow. Furthermore, we propose two additional enhanced approaches to increase the energy saving effects by deferring the triggering action of the high-priority upstream packet as well as coalescing new arrival packets during waiting time into the same scheduling cycle.