Dejitter Buffer Drift Measurement for r-PHY Timing Holdover
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Solution Overview
Problem
In distributed access architectures (DAA) of cable television networks, remote devices struggle to accurately measure the amount of drift relative to the core during holdover periods, leading to potential loss of synchronization and offline cable modems.
Innovation Solution
A remote device measures buffer depth fluctuations and applies low-pass filtering to distinguish between network jitter and frequency drift, calculating fractional frequency offset and phase drift to determine when holdover exceeds specified thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If timing synchronization is maintained using a reference signal from a base station, then timing accuracy is improved, but the system becomes vulnerable to reference signal interruptions and attacks
Solution Approach 1:
The patent introduces a timing adjustment value as an intermediary mechanism. Instead of directly relying on the reference signal from the base station, the UE uses a stored timing adjustment value to compensate for timing deviations. This intermediary allows the system to maintain accurate timing even when the reference signal is interrupted or attacked, as the timing adjustment value serves as a buffer that can be updated when reference signals are available and applied continuously to maintain synchronization.
Solution Approach 2:
The patent implements preliminary action by storing the timing adjustment value in advance before reference signal interruptions occur. The UE maintains a stored timing adjustment value that was obtained during periods when reference signals were available. This pre-stored value enables the UE to continue accurate timing synchronization even when the reference signal is subsequently interrupted or attacked, as the compensation mechanism is already in place and does not require real-time reference signal availability.
Data Source
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AI summary
Systems and methods for measuring the amount of drift of a clock in a remote device relative to a clock in a core, both in a distributed access architecture, by measuring the change in fullness of a dejitter buffer in the remote device that holds data provided from the core.