A low-overhead switched-mode Energy saving strategy for OFDMA-PON downstream transmission

Abstract Green networks and energy saving have become important topics of worldwide concern and attracted intensive attention from both academia and industry. As orthogonal frequency division multiplexing access passive optical network (OFDMA-PON) employs more advanced and energy-consuming digital signal processing (DSP) techniques than other PON systems, it is of critical importance to improve the energy efficiency of OFDMA-PONs. In this paper, we propose a switched-mode energy saving strategy with low overhead for OFDMA-PON downstream transmission. By embedding information in the short training sequences (STSs) of the OFDM frame preamble, the STSs serve a twofold purpose: providing time synchronization and carrying the information with regard to the destination of the frame, hence eliminating the need for extra upper-layer control or information exchange between OLT and ONU. As STS is an inherent part of the OFDM frame, the proposed scheme requires little extra overhead in transmission time and hardware cost. The ONU continues the subsequent processing only when it is the intended receiver, while the unintended ONUs drop the frame and stands by to save energy. In order to achieve a tradeoff between energy saving and delay performance, the scheme switches between single-ONU mode and team mode where either a single ONU or a team of ONUs are the targeted receivers. We verify the feasibility of proposed scheme through experiments and evaluate the performance in terms of energy saving and packet delay by simulations. The results indicate that substantial energy can be saved compared with conventional OFDMA-PON systems.