Detecting Path Delay Asymmetry in Communication Networks
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Solution Overview
Problem
Current timing protocols, such as PTP and CPRI, face challenges in accurately detecting changes in path delay asymmetry between nodes in a communications network, which can lead to incorrect synchronization and potential loss of traffic in applications like WCDMA and LTE, as they often require three independent synchronization references and are costly and time-consuming to calculate.
Innovation Solution
A method that determines if a timing reference received by a slave node indicates a significant time correction greater than a threshold, and checks if other slave nodes also received similar corrections, allowing for the detection of path delay asymmetry changes without needing three independent references, using a network control entity to communicate with multiple domains and apply appropriate corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If path delay asymmetry is calculated prior to network start-up using traditional methods, then initial synchronization is achieved, but the system cannot detect changes in path delay asymmetry that occur after start-up
Solution Approach 1:
The patent performs preliminary calculation of path delay asymmetry before network start-up, establishing a baseline value. This preliminary action enables the system to later detect changes by comparing current measurements against the pre-established baseline, resolving the contradiction between having initial synchronization capability and the ability to detect subsequent changes.
Solution Approach 2:
The patent implements a feedback mechanism where the master node continuously monitors timing references from slave nodes and compares current path delay measurements against the pre-calculated asymmetry values. This feedback loop enables detection of changes in path delay asymmetry that occur after network start-up, maintaining synchronization accuracy while adapting to network changes.
2Measurement precision
If three independent synchronization references are used to detect path delay asymmetry changes, then detection accuracy is improved, but device complexity and calculation cost increase significantly
Solution Approach 1:
The patent extracts and utilizes only the essential timing reference information needed for detection from the slave nodes. Instead of requiring three independent synchronization references, the system extracts timing data from a single timing reference message and compares it against the pre-calculated path delay asymmetry baseline, significantly reducing device complexity while maintaining detection capability.
Solution Approach 2:
By pre-calculating and storing path delay asymmetry values before network operation, the patent eliminates the need for complex real-time calculations involving multiple independent references. The preliminary action of establishing baseline values simplifies the ongoing detection process to straightforward comparisons, reducing both device complexity and calculation costs.
3Measurement precision
If timing correction threshold is set low for sensitive detection, then detection sensitivity is improved, but false detections increase
Solution Approach 1:
The patent prepares compensatory measures in advance by pre-calculating path delay asymmetry values and establishing them as baselines. This beforehand cushioning enables the system to distinguish between normal variations and actual path delay changes, allowing for sensitive detection while minimizing false detections through comparison against the pre-established baseline rather than using arbitrary thresholds.
Data Source
AI summary
A method for detecting a timing reference affected by a change in path delay asymmetry in a communications network comprising a master node having a master clock and a plurality of slave nodes each having a respective slave clock is provided. The method comprises: determining that a first timing reference received by a first slave node indicates a time correction to its slave clock greater than a time correction threshold; determining whether one or more other slave nodes have received a timing reference indicating a time correction to their slave clock greater than a time correction threshold; and determining whether the first timing reference is affected by a change in path delay asymmetry based on the determining of whether one or more other slave nodes have received a timing reference indicating a time correction to their slave clock greater than a time correction threshold. Apparatus and a computer program for detecting a timing reference affected by a change in path delay asymmetry in a communications network are also provided.