PON Protection Maintenance Link for Standby OLT RTT Synchronization
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Solution Overview
Problem
In passive optical networks (PONs), the process of switching over to a standby OLT during failures is time-consuming due to the need for ranging and updating network information, leading to service interruptions and inefficiencies, especially when the active and standby OLTs are geographically remote or when network topology changes occur.
Innovation Solution
Establishing a protection maintenance link between active and standby OLTs for continuous measurement and synchronization of round-trip time (RTT) values, allowing the standby OLT to calculate new RTT values without performing a ranging process, enabling seamless switch-over and minimizing service disruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the standby OLT performs ranging process during switch-over to ensure accurate RTT measurement, then measurement precision is improved, but service interruption time increases
Solution Approach 1:
The invention performs RTT measurement and ranging operations in advance during normal operation, before any failure occurs. The active OLT continuously measures RTT values and maintains them in a buffer. When switch-over is needed, the standby OLT already has pre-calculated RTT values, eliminating the need for time-consuming ranging during the actual switch-over event.
Solution Approach 2:
The invention creates a copy of the RTT measurement functionality by having the standby OLT receive and store RTT values measured by the active OLT. This allows the standby OLT to use these copied values immediately upon activation without performing new measurements, thus reducing switch-over time while maintaining accuracy.
2Adaptability or versatility
If the standby OLT maintains updated network information continuously, then adaptability to topology changes is improved, but use of energy and processing resources increases
Solution Approach 1:
The invention merges the RTT measurement function into the regular data communication traffic. The same communication channels used for normal PON operations are also used to transmit RTT measurement signals and maintain updated network information. This eliminates the need for separate dedicated measurement operations, reducing energy consumption while maintaining adaptability.
3Reliability
If a protection maintenance link is established between active and standby OLTs for continuous RTT synchronization, then reliability of switch-over is improved, but device complexity increases
Solution Approach 1:
The invention makes the protection maintenance link multi-functional by using it for both regular data communication and RTT measurement/synchronization. The same physical infrastructure serves dual purposes, reducing the need for additional dedicated protection channels and thereby limiting the increase in device complexity while maintaining high switch-over reliability.
Data Source
AI summary
A method for performing a protection in passive optical networks. The method comprises forming a protection maintenance link between an active optical line terminal (OLT) and a standby OLT; forming a synchronization link between the active OLT and the standby OLT; computing a base differential distance value; continuously measuring round trip time (RTT) values by the active OLT using the protection maintenance link; periodically sending at least RTT values calculated by the active OLT to the standby OLT over the synchronization link; and computing, by the standby OLT, a new RTT value based on at least a RTT value measured by the active OLT and a standby differential distance value, when a switch-over action is triggered, thereby allowing the standby OLT to serve optical network units (ONUs) in the PON without performing a ranging process.