Phase-Adjusted Clock Signal for GPON Upstream Synchronization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current point-to-multipoint networks, specifically Gigabit PONs, face challenges in accurately synchronizing upstream burst transmissions due to variations in timing delays, which can lead to improper recovery of upstream bursts and disruption of network services.
Innovation Solution
A method and apparatus for controlling the timing of upstream transmissions in passive optical networks by determining a core clock signal from downstream transmissions and generating a phase-adjusted transmitter clock signal, ensuring accurate synchronization and alignment with the OLT's timing window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard clock signal is used for upstream transmission timing, then the transmission process is simple, but the upstream bursts cannot be properly synchronized at the OLT due to timing delays
Solution Approach 1:
The patent applies preliminary action by determining the timing delay through ranging procedure before upstream transmission begins. The OLT measures the round-trip time and calculates the one-way delay, then communicates this delay information to the ONU/ONT. This preliminary timing calibration ensures that subsequent upstream bursts are properly synchronized without requiring complex real-time adjustments during transmission.
Solution Approach 2:
The patent changes the clock signal parameter by generating a phase-adjusted clock signal with a specific offset relative to the core clock signal. The transmitter clock signal is derived by adjusting the phase of the core clock based on the determined timing delay, allowing the upstream transmission to be timed correctly for synchronization at the OLT while maintaining a relatively simple transmission process.
2Measurement precision
If timing delay measurement is performed for each ONU/ONT, then synchronization accuracy is improved, but service disruption occurs during the ranging procedure
Solution Approach 1:
The patent segments the ranging procedure into dedicated time slots for different ONUs/ONTs, allowing timing delay measurement to be performed for each device individually. By allocating specific measurement windows and using guard times between measurements, the system can accurately measure timing delays for multiple devices without requiring complete network shutdown, thus maintaining service continuity while achieving precise measurements.
3Manufacturing precision
If the transmitter uses the core clock signal directly, then the system is simple, but bit variance exceeds GPON specification requirements
Solution Approach 1:
The patent changes the clock signal parameter by introducing a phase offset to the core clock signal to generate the transmitter clock signal. This phase adjustment aligns the upstream transmission timing with the OLT's expected reception window, ensuring that bit variance remains within GPON specification limits. The parameter change is implemented through a phase adjustment mechanism that modifies the clock signal's timing characteristics without fundamentally changing the system architecture.
Data Source
AI summary
In a method for controlling timing of a transmission signal from a network termination device having a receiver and a transmitter, a signal is received at the receiver of the network termination device, the signal having been transmitted in accordance with a predetermined bit rate. A core clock signal for the receiver is determined based on the predetermined bit rate at which the signal was transmitted, and the core clock signal is communicated to the transmitter of the network termination device. At the transmitter of the network termination device, a phase adjusted clock signal is generated, and the phase adjusted clock signal is set as the transmitter clock signal. The transmitter clock signal is offset from the core clock signal, and the transmission signal is transmitted from the transmitter of the network termination device based on the transmitter clock signal.