PON Synchronization via Timestamped Message Propagation
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Solution Overview
Problem
Current network systems face challenges in synchronization, particularly in passive optical networks (PON), where existing synchronization techniques are expensive, risky for upgrades, and perform poorly, especially for Time of Day (ToD) synchronization in applications like cellular tower backhaul and femto-cell deployments.
Innovation Solution
A method involving a network system with a master and slave network unit that calculates and synchronizes time by sending a master message with round trip time and local time, allowing slave network units to calculate their local time based on received messages and delays, ensuring accurate time synchronization across the network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If IEEE 802.1AS synchronization technique is introduced, then synchronization performance is improved, but equipment cost and upgrade risk increase
Solution Approach 1:
The patent uses message copying and timestamping techniques where synchronization information is propagated through copied messages (PMT, SYNC messages) containing timestamps. Each network element creates copies of synchronization messages with its own timing information, enabling distributed synchronization without requiring complex dedicated hardware at each node.
Solution Approach 2:
The patent replaces mechanical/physical synchronization methods (GPS receivers, dedicated hardware clocks) with electronic/software-based timestamping and message-passing mechanisms. The synchronization is achieved through software protocols (IEEE 1588 PTP, IEEE 802.1AS) that use standard network communications rather than specialized mechanical timing equipment.
2Measurement precision
If IEEE 1588 over PON is used, then Time of Day synchronization is attempted, but performance deteriorates
Solution Approach 1:
The patent segments the synchronization process into distinct phases: one-way delay measurement (OWDM), two-way delay measurement (TWDM), and time stamping. Each phase handles specific aspects of synchronization independently, allowing precise ToD calculation while maintaining overall system reliability through modular error handling and validation at each segment.
Solution Approach 2:
The patent introduces intermediary synchronization messages (PMT - Physical Layer Message, SYNC messages, FOLLOWUP messages) that act as mediators between master and slave clocks. These intermediary messages carry timestamp information through the PON network, enabling accurate ToD synchronization by providing intermediate reference points that bridge the master-slave clock relationship.
3Measurement precision
If GPS frequency standards are deployed at cellular towers, then synchronization accuracy is improved, but network cost increases
Solution Approach 1:
The patent makes the optical network infrastructure universal by enabling it to serve dual purposes: data transmission and time distribution. The same PON infrastructure that carries traffic also carries synchronization messages, eliminating the need for separate GPS equipment at each cell tower. The network performs multiple functions (data + timing) using the same physical medium.
Solution Approach 2:
The patent enables the network to self-synchronize by having network elements (OLT, ONU/ONT) automatically exchange timestamped messages and calculate delays autonomously. The system performs its own synchronization without external GPS intervention, with each node contributing to and benefiting from the collective timing information through self-organizing protocol execution.
Data Source
AI summary
A method of operation of a network system including a network line terminal coupled to a slave network unit and a master network unit over a first network includes: calculating a master round trip time between the network line terminal and the master network unit; sending a master message to the slave network unit, the master message having the master round trip time and a master local time; and calculating a slave local time based on the master round trip time and the master local time.