UE Clock Synchronization Accuracy in NR IIOT
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Solution Overview
Problem
In NR IIOT, maintaining finer synchronicity between the Time-Sensitive Networking Grand Master (TSN GM) clock and User Equipment (UE) clocks is challenging due to UE clock drift caused by crystal oscillator inaccuracy and varying propagation delays, which can lead to failures in achieving the required 1 μs synchronization accuracy.
Innovation Solution
A method that involves receiving reference time information and Timing Advance (TA) commands from a gNB node, calculating Propagation Delay (PD), and updating the UE clock only when accurate PD is ensured, either at the time of reference time information reception or upon receipt of an updated TA command, to maintain synchronization accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reference time information is transmitted periodically from gNB to correct UE clock drift, then clock synchronization is maintained, but propagation delay variations cause synchronization accuracy to deteriorate
Solution Approach 1:
The patent applies preliminary action by having the gNB transmit timing advance commands to the UE in advance of when propagation delay variations will affect synchronization accuracy. The gNB proactively adjusts the UE's transmission timing based on predicted or measured delay changes, preventing synchronization errors before they occur rather than correcting them after detection.
Solution Approach 2:
The patent implements feedback mechanisms where the gNB monitors propagation delay variations and sends timing advance commands back to the UE to compensate for detected changes. This closed-loop feedback system continuously adjusts UE transmission timing based on real-time channel conditions, maintaining synchronization accuracy despite varying propagation delays.
2Loss of time
If UE clock update is applied immediately upon receiving reference time information, then synchronization response time is improved, but inaccurate propagation delay compensation causes synchronization error
Solution Approach 1:
The patent applies preliminary action by pre-calculating or pre-determining the timing advance value before the UE clock update is applied. The gNB prepares the timing advance command in advance based on measured or predicted propagation delay, so that when the UE receives the reference time information, the correction value is already ready and accurate, enabling immediate update without waiting for additional measurements.
Solution Approach 2:
The patent uses beforehand cushioning by applying a margin or buffer to the timing advance calculation to account for potential variations in propagation delay. This preventive cushion ensures that even if delay conditions change slightly, the synchronization remains within acceptable accuracy bounds, protecting against future errors.
3Reliability
If timing advance command is transmitted frequently to compensate for propagation delay changes, then synchronization accuracy is improved, but signaling overhead and system complexity increase
Solution Approach 1:
The patent applies partial action by transmitting timing advance commands only when propagation delay variations exceed a certain threshold, rather than sending updates continuously or excessively frequently. This selective approach maintains synchronization accuracy for significant changes while reducing unnecessary signaling overhead for minor variations that are within acceptable tolerance ranges.
Solution Approach 2:
The patent implements periodic action by transmitting timing advance commands at regular intervals or based on periodic channel measurements, rather than continuously monitoring and signaling every change. This periodic approach balances synchronization maintenance with reduced signaling complexity, updating only when the periodic schedule dictates or when measurements indicate a need for adjustment.
Data Source
AI summary
A method for maintaining finer synchronicity requirement (e.g. less than 1 μs synchronicity) between sync master clock and UE clock in NR IIOT is disclosed. The present disclosure introduces a method to apply the UE clock update depending on the UL timing advance reception time. The present disclosure also introduces a new signaling to indicate scheduling request ID for propagation delay change and based on which triggering timing advance to maintain the finer synchronicity requirement between sync master and UE clock. This disclosure also introduces a new method to compute the propagation delay change at UE, and thereby performing propagation delay compensation to maintain finer synchronicity requirement between sync master and UE clock.