Multi-power-level energy saving management for passive optical networks

Environmental concerns have motivated network designers to further reduce energy consumption of access networks. This paper focuses on reducing the energy consumption of the Ethernet passive optical network (EPON) as one of the most efficient transmission technologies for broadband access. In the EPON, downstream traffic is sent from the optical line terminal (OLT) located at the central office to all optical network units (ONUs). Each ONU checks all arrival downstream packets and selects the downstream packets destined to itself. Therefore, receivers at ONUs have to always stay awake, thus consuming a large amount of energy. On the other hand, an ONU transmitter can be triggered by the arrival of upstream traffic, so it can go to the low power mode when no traffic is observed. Putting ONUs into the low power mode during light traffic is a known strategy for energy saving. In this article, we address the downstream challenge and also improve the ONU transmitter sleep time by proposing a simple sleep control scheme. We also propose an upstream and a downstream sleep-aware traffic scheduling scheme to avoid missing packets during the sleep states. The proposed sleep control scheme does not need the handshake process and is based on the mutual inference at the OLT and the ONU. Simulation results show that the proposed scheme can save energy by as much as 60% when network traffic is light.