PWC-PON: An Energy-Efficient Low-Latency DBA Scheme for Time Division Multiplexed Passive Optical Networks

Reducing network energy consumption and offering low-latency service quality have been the pursued goals in broadband passive optical networks (PONs). To realize these goals, energy-efficient dynamic bandwidth allocation (DBA) has been extensively studied. Nevertheless, few of these DBA schemes can effectively support low-latency and low-energy requirements, simultaneously. For these existing DBA schemes, the adopted energy-saving methods by sleeping some network elements would not handle the mismatch between the upstream and downstream bandwidth required by an optical network unit (ONU), which brings in a longer active window for each ONU and thus larger packet latencies. In this paper, an energy-efficient low-latency DBA scheme is proposed based on a novel pairwise combination (PWC) method. The essence of the PWC method is to compact the polling cycle length as much as possible by dynamically paring any two ONUs in complementary ways, which in turn also improves latency performance of data packets (i.e., quality of service (QoS)). Moreover, we introduce a multiple-state energy-saving mode into the proposed DBA scheme to reduce the PON energy consumption, with the consideration of both the upstream (US) and downstream (DS) transmissions. We establish an energy saving model for the proposed PWC-PON compared with the PONs with the existing DBA schemes, and also present a comprehensive M/G/1 queuing analysis with modification for the data latency performance. Extensive theoretical analysis and simulation results show that the proposed PWC-PON can reduce US and DS latency by 50% compared with the existing Gate Service (GS)-based DBA scheme. The energy saving efficiency is up to 3.5% higher than the benchmark when the US traffic load is light. It suggests that our PWC-based DBA scheme cannot only reduce the energy consumption, but also reduce the packet latency for PON system.