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 article, 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.
Highlights
In recent years, increasing demands from network users and advanced applications have prompted access networks undergone a rapid development [1]
By polling the Optical Network Units (ONUs) following the ascending sequence of ONU propagation delays, the masking performance can be improved, and the channel utilization efficiency of the shortest propagation delay (SPD) scheme is enhanced compared with the original Interleaved Polling with Adaptive Cycle Time (IPACT) scheme
We investigated how polling sequence and polling cycle length affect the energy efficiency of ONUs and proposed a dynamic polling sequence arrangement scheme as well as a polling cycle compressing scheme for energy-efficient Ethernet passive optical network (EPON) [22], [23]
Summary
In recent years, increasing demands from network users and advanced applications have prompted access networks undergone a rapid development [1]. ONU propagation delays masking reduces polling cycle time and improves channel utilization, and packet delay performance can be benefited as short polling cycle time means short queueing delay. By polling the ONUs following the ascending sequence of ONU propagation delays, the masking performance can be improved, and the channel utilization efficiency of the SPD scheme is enhanced compared with the original IPACT scheme. The two schemes are compared in terms of polling cycle time, packet delay, and energy efficiency in transmitting low-latency data, and their practical values are discussed by envisioning the cost-saving tradeoff.
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