OLT Bandwidth Scheduling for ONU Low-Power Windows
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Solution Overview
Problem
Current low-power management modes in passive optical networks (PONs) are inefficient due to latency and jitter introduced by secondary messaging for transitioning to and from low-power modes, especially in medium to high traffic conditions, and are applied conservatively due to limited temporal scope of decision-making at the optical network units (ONUs).
Innovation Solution
An optical line terminal (OLT) dynamically assigns bandwidths and notifies optical network units (ONUs) about low-power opportunities within future DBA intervals, allowing them to switch to and from low-power modes without latency, using existing DBA engine information and extended traffic knowledge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If ONUs use current low-power management modes with secondary messaging for transitioning, then power consumption is reduced during minimal traffic, but latency and jitter are introduced that significantly affect quality of service when traffic increases
Solution Approach 1:
The OLT performs preliminary action by determining low-power opportunities in advance for the next DBA interval and notifying ONUs before the interval begins. This allows ONUs to proactively transition to low-power mode without waiting for traffic conditions to deteriorate, eliminating the need for reactive secondary messaging and preventing QoS degradation.
Solution Approach 2:
The OLT acts as an intermediary by centralizing the determination of low-power opportunities based on its extended traffic knowledge. Instead of individual ONUs making conservative decisions based on limited local information, the OLT coordinates power management across the network, optimizing both energy savings and QoS through centralized control.
2Ease of operation
If ONUs make low-power mode decisions based on limited temporal scope and local traffic information, then decisions are conservative and easy to implement, but potential power savings are limited
Solution Approach 1:
The OLT's DBA engine performs multiple functions: it continues its existing bandwidth allocation tasks while simultaneously determining low-power opportunities. This multi-functionality allows the system to leverage existing traffic knowledge and processing capabilities without adding separate decision-making infrastructure, maintaining ease of operation while maximizing power savings.
Solution Approach 2:
The OLT uses feedback from its bandwidth allocation decisions to identify low-power opportunities. By analyzing which frames do not require ONU transmission, the OLT feeds back this information to ONUs, enabling them to make informed power management decisions based on actual network conditions rather than conservative local estimates.
3Use of energy by moving object
If low-power modes are applied during extended periods of minimal traffic, then energy savings are achieved, but the modes are non-functional in medium to high traffic conditions
Solution Approach 1:
The low-power opportunity determination is dynamic and adapts to current traffic conditions. The OLT calculates low-power opportunities based on actual bandwidth allocation requirements for each DBA interval, allowing the system to automatically adjust between maximizing power savings during low traffic and ensuring full functionality during medium to high traffic without manual intervention.
Solution Approach 2:
The system changes the parameter of ONU operational state based on dynamically determined low-power opportunities. By notifying ONUs of specific frames where low-power mode can be applied, the system enables flexible parameter changes in ONU behavior that adapt to varying traffic conditions, maintaining both energy savings and functional adaptability.
Data Source
AI summary
An optical line terminal, OLT, configured to communicate in a passive optical network, PON, with optical network units, ONUs; wherein the OLT comprises a dynamic bandwidth assignment, DBA, engine configured to dynamically assign bandwidths to traffic-bearing entities within the ONUs for a future DBA interval by allocating transmission opportunities to the traffic-bearing entities within one or more frames of the future DBA interval; wherein a DBA interval includes at least two successive frames; and the OLT is configured to notify, at the latest at the start of a next DBA interval, the respective ONUs about one or more low-power opportunities during the next DBA interval; wherein low-power opportunities are periods of one or more successive frames during the next DBA interval without transmission opportunities allocated to the traffic-bearing entities of a respective ONU.