Study on the Solutions to Heterogeneous ONU Propagation Delays for Energy-Efficient and Low-Latency EPONs

Abstract

The scattered Optical Network Units (ONUs) in an optical access network have different propagation delays. In an Ethernet passive optical network (EPON) adopting the traditional Interleaved Polling with Adaptive Cycle Time (IPACT) scheme, such ONU propagation delay difference will waste network resources and will degrade both network delay performance and network energy efficiency in delivering low-latency services. In this paper, to deal with the heterogeneous ONU propagation delays problem, two solutions are proposed and investigated. The first solution, namely the Upstream Postponing with ONU Dozing (UP-OD) scheme, is to properly postpone the upstream transmissions of those ONUs having relatively short propagation delays to improve channel utilization efficiency, and ONU doze mode is incorporated to enhance network energy efficiency. The second solution, namely the Identical Fiber Length with ONU Sleeping (IFL-OS) scheme, is to adopt an identical distribution fiber length for ONUs to enhance channel utilization, and ONU sleep mode is incorporated for energy consumption reduction. Simulation results show that both the UP-OD scheme and the IFL-OS scheme reduce network delay and improve network energy efficiency in delivering low-latency (<1 ms) data, and the IFL-OS scheme shows lower energy consumption in transmitting per bit of low-latency (<1 ms) data compared with the UP-OD scheme. Further practical value discussion shows that for the case of serving services requiring 1 ms delay, the UP-OD scheme is suitable for applying in the 1G-EPONs, whereas the IFL-OS scheme is considerable for the 10G-EPONs.

Bandwidth Prediction Based Resource Allocation Scheme for Low-Latency and Energy-Efficient PONs With Heterogeneous ONU Propagation Delays

“…To deal with this issue, the shortest propagation delay first scheduling scheme was proposed in [18], which prioritized ONUs with short propagation delays when polling ONUs. Also, in our previous work, we proposed an US transmission postponing based scheme to deal with the heterogeneous ONU propagation delays issue, which appropriately postponed the US transmissions of those ONUs with relatively short propagation delays to reduce the channel idle time [19]. Aiming at reducing the channel idle time at the OLT side between consecutive polling cycles for long-reach (100+km) application scenarios, the multi-threaded polling schemes were proposed in [20] and [21], in which concurrent polling operations were employed through the creation of multiple threads while dynamically adjusting bandwidth allocation based on real-time network conditions.…”

Energy Conservation in Passive Optical Networks: A Tutorial and Survey

“…It is worth noting that different types of sleep mode can have different transition periods and energy saving trade-off. For example, in the doze mode of a 1G EPON ONU, the transition period is approximately 1 µs; however, power consumption is 1.7 W [260].…”

Energy-Efficient Regional Area Metropolitan Optical Access Network (RAMOAN) Using Modified Load Adaptive Sequence Arrangement (M-LASA) Methodology

“…Te presented approach exploits the energy efciency of EPONs in the downstream transmission and builds a holistic model to defne the sleep periods and enhance energy efciency. Te propagation delay in EPON's scattered optical network units is analyzed in [15] using interleaved polling and an adaptive cycle time scheme to improve energy efciency in low latency services. Te presented approach initially introduces an upstream, postponing with ONU dozing to postpone the upstream transmissions that introduce delay.…”