Phase Offset Estimation Using Delay Asymmetry
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing timing synchronization methods, such as IEEE 1588 PTP, face errors in phase offset estimation due to asymmetry in communication path delays, particularly variable queuing delays, which are not accurately accounted for in current approaches.
Innovation Solution
A method that estimates the phase offset of a local clock by accounting for queuing asymmetry through direct input into an estimation algorithm, such as a Kalman filter, using queuing asymmetry measures calculated from timestamp differences to improve accuracy and reduce errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If symmetrical path delay assumption is used in phase offset estimation, then calculation complexity is reduced, but measurement precision deteriorates due to queuing delay asymmetry
Solution Approach 1:
The patent replaces the traditional mechanical assumption of symmetrical path delays with a computational model that calculates asymmetry using timestamp differences. By substituting the simple symmetry assumption with a calculation-based approach using T1, T2, T3, T4 timestamps, the system achieves higher measurement precision without excessive complexity increase.
Solution Approach 2:
The patent introduces an intermediary calculation step that computes path delay asymmetry using timestamp differences from PTP message exchanges. This intermediary measure serves as a mediator between the raw timestamps and the final phase offset estimation, allowing the system to account for queuing delays while maintaining algorithmic efficiency through the use of this intermediate asymmetry value.
2Measurement precision
If queuing asymmetry measures are directly incorporated into estimation algorithm, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent changes the parameters fed into the estimation algorithm by incorporating the calculated path delay asymmetry measure alongside the timestamp differences. This parameter modification allows the Kalman filter or other estimation algorithms to compensate for queuing delays, improving measurement precision while maintaining algorithmic structure and avoiding excessive complexity increases.
3Measurement precision
If timestamp recording is performed for all messages in window, then measurement precision is improved, but loss of time increases due to processing overhead
Solution Approach 1:
The patent performs preliminary timestamp recording at the moment of message sending and reception, capturing T1, T2, T3, T4 values immediately when events occur. This preliminary action ensures high measurement precision is achieved without requiring additional processing time later, as the critical timing data is captured in real-time during message exchange rather than through subsequent analysis.
Data Source
AI summary
This invention relates to methods and devices for timing synchronization. The invention has particular application where timing is being carried out over packet networks using, for example, the IEEE 1588 Precision Time Protocol (PTP). Embodiments of the invention make use of estimated forward and reverse path delay asymmetries directly in the estimation algorithm (for example a Kalman filter). This can allow the variation in the timestamps which have been compensated for the delay asymmetry to be significantly reduced, which can reduce the complexity of the phase offset estimation algorithm.