One-Way Delay Measurement Clock Skew Elimination
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Solution Overview
Problem
Existing methods for determining clock offset between network components in packet switched networks fail to accurately account for relative clock skew, leading to inaccuracies in one-way and round-trip-time delay measurements due to frequency variations in local clock oscillators, which are exacerbated by network and processing delays.
Innovation Solution
A method combining the Improved Cristian Algorithm with linear interpolation to correct systematic errors in one-way delay measurements, using parameters calculated from the ICA to improve measurement accuracy by eliminating the first derivative of time differences between systems, thereby enhancing the precision of clock synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the Improved Cristian Algorithm is used to determine clock offset, then the measurement precision is improved, but the systematical error due to relative clock skew remains uneliminated
Solution Approach 1:
The patent applies preliminary action by calculating clock offset values at the beginning and end of the measurement interval before performing the actual delay measurements. These preliminary offset values are then used to correct the measured delays, eliminating systematical errors before they affect the final results.
Solution Approach 2:
The patent implements feedback by using the measured one-way delays to calculate clock offset values, which are then fed back to correct the original measurements. The correction process uses the relationship between forward and backward one-way delays to continuously improve measurement accuracy.
2Ease of operation
If one-way delay measurements are performed without correction, then the measurement process is simple, but the accuracy is degraded due to clock skew
Solution Approach 1:
The patent extracts and removes the systematical error component (clock skew) from the measured one-way delays. By separating the error component from the actual delay measurement, the patent maintains measurement simplicity while improving accuracy through post-measurement correction.
Solution Approach 2:
The patent changes the parameter representation by introducing corrected delay values that account for clock offset variations. The measurement process remains simple, but the results are transformed into a corrected form that eliminates systematical errors through parameter adjustment.
3Device complexity
If clock offset is determined only at the beginning of measurement interval, then the calculation complexity is reduced, but the accuracy is degraded due to changing clock skew
Solution Approach 1:
The patent segments the measurement interval into multiple points (beginning, middle, end) and calculates clock offset values at each segment boundary. This segmentation allows the system to account for clock skew variations throughout the measurement period without requiring complex continuous correction models.
Solution Approach 2:
The patent performs preliminary clock offset calculations at the beginning and end of the measurement interval before the actual delay measurements. These preliminary actions establish reference points that simplify the correction process while improving accuracy compared to single-point determination.
Data Source
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AI summary
The invention describes a method for eliminating systematical errors in one-way delay (OWD) measurements between two or more computing systems (10) in a communication network. The proposed invention extends the recent state of the art of high-precise OWD measurements, and has the advantage of elimination of the first derivative of the time difference between two computing systems (known as relative clock skew) by means of applying interpolation to one-way delay measurement results at each measurement point between tw reference points. The thus determined interpolation value corresponds to a clock offset and is deducted from the actual measurement result, thereby eliminating the relative clock skew in the measurement result set. This allows for much finer resolution of finding trends and/or over time developments in the measurement result set. The invention further concerns an apparatus to perform the method according to the invention and a corresponding computer program product.