Two-Way Delay Error Compensation in PTP Optical Networks
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Solution Overview
Problem
In communication systems, particularly in mobile networks evolving to 4G and 5G, two-way delay errors in physical connections between PTP master and slave devices lead to inaccuracies in clock synchronization, especially over long optical fiber connections, where traditional methods like GNSS face installation costs and indoor reception issues.
Innovation Solution
The method involves setting specific wavelengths for signal transmission using Precision Time Protocol (PTP) to identify key time points, calculating a delta value for two-way delay errors, and applying a compensation value to correct the time offset, thereby enhancing synchronization accuracy without requiring separate hardware or software, making it applicable over various distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GNSS signals are used for synchronization, then synchronization can be achieved, but installation costs increase and indoor installations become problematic
Solution Approach 1:
The patent introduces an intermediary mechanism (optical fiber connection with wavelength-based measurement) to transfer time synchronization between master and slave devices, replacing the need for direct GNSS signal reception at each device. This intermediary approach allows synchronization to be achieved through the communication medium itself, eliminating the need for expensive and complex GNSS installations while maintaining reliability.
2Device complexity
If traditional PTP is used without wavelength-based compensation, then the system is simpler, but two-way delay errors occur over long optical fiber connections
Solution Approach 1:
The patent changes the measurement parameter from standard PTP packet timing to optical wavelength-based timing. By measuring the time of flight using optical wavelengths (λ1 and λ2) in both directions, the system can calculate and compensate for two-way delay errors. This parameter change enables precise measurement of propagation delays over long optical fiber connections without significantly increasing system complexity.
3Measurement precision
If wavelength-based two-way delay measurement is implemented, then time offset accuracy improves, but the system becomes more complex
Solution Approach 1:
The patent makes the communication medium serve multiple functions: it simultaneously carries data traffic and performs timing measurement. The optical fiber connection that already exists for data communication is also used for wavelength-based time of flight measurement. This multi-functionality approach improves measurement precision without requiring separate dedicated measurement hardware, thereby limiting the increase in system complexity.
Data Source
AI summary
Proposed is an operation method for two-way delay error compensation, the method including first to sixth steps. In the first step, a first wavelength is set as a signal wavelength for a master and a third wavelength is set as a signal wavelength for a slave. In the second step, first, second, third, and fourth time points are identified by using PTP. In the third step, a second wavelength is set as a signal wavelength for the master and the second wavelength is set for the slave. In the fourth step, fifth, sixth, seventh, and eighth time points are identified by using the PTP. In the fifth step, a delta value for a two-way delay error is identified on the basis of the first to eighth time points. In the sixth step, a compensation value of the two-way delay error is identified on the basis of the delta value.