Radio Link Monitoring Accuracy on Unlicensed Spectrum
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Solution Overview
Problem
In the new radio (NR) system, terminal devices face challenges in accurately determining channel conditions when the quality of reference signals is poor, as they cannot distinguish between channel busyness and poor terminal device channel quality, leading to misjudgments of radio link failures during wireless link monitoring on unlicensed spectra.
Innovation Solution
The terminal device determines whether to stop a timer T310 based on the proportional relation between in-sync (IS) and out-of-sync (OOS) indications, updating these counts over time durations or specific thresholds to avoid misjudgments caused by busy channels, thereby improving the accuracy of radio link monitoring measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the terminal device uses traditional RLM measurement based on reference signal quality, then the measurement process is simple, but the accuracy of channel condition determination deteriorates because the device cannot distinguish between channel busyness and poor channel quality
Solution Approach 1:
The patent segments the RLM measurement process into two independent parts: (1) reference signal quality measurement, and (2) channel busy detection through uplink transmission attempts. This segmentation allows the terminal to separately evaluate channel quality and channel availability, resolving the inability to distinguish between poor quality and busy channel conditions while maintaining manageable complexity through modular measurement approaches
Solution Approach 2:
The patent introduces an intermediary mechanism - the uplink transmission attempt and its acknowledgment - that mediates between the terminal device and the channel condition assessment. By attempting uplink transmission and checking for acknowledgments, the terminal indirectly determines channel busyness without directly measuring it, enabling accurate differentiation between channel quality and channel availability issues
2Reliability
If the terminal device continuously monitors reference signal quality to detect radio link failures, then the monitoring coverage is comprehensive, but false failure determinations increase due to inability to differentiate channel busyness from actual link degradation
Solution Approach 1:
The patent applies preliminary action by having the terminal device attempt uplink transmission before finalizing radio link failure determination. This preliminary uplink attempt serves as an additional verification step that precedes the failure declaration, allowing the device to check whether the channel is merely busy rather than actually degraded, thereby preventing false failure determinations while maintaining comprehensive monitoring coverage
Solution Approach 2:
The patent implements feedback mechanisms where the terminal monitors both reference signal quality and uplink transmission acknowledgments. This dual-feedback approach provides comprehensive information about channel conditions, enabling the device to distinguish between temporary channel busyness (indicated by missing acknowledgments but potentially good reference signal quality) and actual link degradation (indicated by poor reference signal quality), thus improving reliability and reducing false failures
Data Source
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AI summary
The present application discloses a method and a terminal device for wireless link monitoring, which can improve an accuracy of wireless link monitoring on unlicensed spectrum. The method includes: starting, by a terminal device, a timer T310, when a number of out of sync (OOS) indications continuously received by the terminal device exceeds a first number N310; and determining, by the terminal device, whether to stop the timer T310 before the timer T310 expires, according to a number of in sync (IS) indications received after the timer T310 is started or according to a proportional relation between the IS indication and the OOS indication received after the timer T310 is started.