Harmonized Radio Link Monitor and Beam Failure Recovery
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Solution Overview
Problem
In Millimeter Wave (mmWave) beamforming new radio systems, the short transmission path lifetime and vulnerability to environmental changes and user equipment movements lead to beam failures, necessitating improved harmonization between radio link monitor and beam failure recovery mechanisms to maintain link quality.
Innovation Solution
A method is proposed where a counter is initiated to count Out-of-Sync (OOS) indications upon unsuccessful beam failure recovery to trigger early Radio Link Failure (RLF) declaration or reset the Radio Link Monitor (RLM) procedure, ensuring accurate link quality maintenance by interacting between the beam failure recovery (BFR) and RLM procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If beam failure recovery procedure is implemented to handle beam tracking issues, then beam alignment reliability is improved, but the interaction complexity between beam failure recovery and radio link monitor procedures increases
Solution Approach 1:
The patent merges the beam failure recovery procedure and radio link monitor procedure into a unified harmonized operation framework. The UE integrates BFR and RLM procedures by sharing common resources (beam failure recovery request resources, candidate beam identifiers) and coordinating their operations through a unified decision-making mechanism that determines when to initiate BFR versus when to declare RLF based on combined assessment of beam failure conditions and radio link quality metrics.
Solution Approach 2:
The patent introduces an intermediary coordination mechanism that mediates between the BFR procedure and RLM procedure. This intermediary layer assesses both beam failure conditions and radio link quality, then makes coordinated decisions about whether to initiate beam failure recovery or declare radio link failure, preventing conflicting actions and reducing overall system complexity.
2Measurement precision
If the number of OOS indications threshold is lowered for early RLF declaration, then link quality maintenance accuracy is improved, but the false alarm rate increases
Solution Approach 1:
The patent dynamically adjusts the threshold parameters for OOS indications based on the operational state of the system. When beam failure recovery is successfully initiated, the patent modifies the RLM evaluation parameters to account for the ongoing recovery process, temporarily raising the threshold for RLF declaration to avoid false alarms during legitimate recovery attempts. This adaptive parameter adjustment maintains measurement precision while reducing false alarm rates.
3Measurement precision
If beam tracking operation is continuously adapted to channel changes, then beam alignment accuracy is improved, but the signaling overhead and processing complexity increase
Solution Approach 1:
The patent implements periodic beam tracking operations rather than continuous adaptation. The UE performs beam tracking at configured intervals and only initiates beam failure recovery when beam failure conditions are detected between periodic measurements. This periodic approach maintains beam alignment accuracy while significantly reducing signaling overhead and processing complexity compared to continuous tracking.
Data Source
AI summary
A method for harmonized operation between radio link monitor and beam failure recovery is proposed. In one example, upon indication of unsuccessful recovery from beam failure, a counter is initiated to count a configured number of OOS indication before RLF is declared due to beam failure. In another example, upon indication of successful recovery from beam failure, a counter is initiated to count a configured number of IS indication before starting over RLM procedure on its previous observations on failed beams. As a result, either early RLF declaration or RLM reset may be triggered based on BFR procedure to more accurately maintain the link quality.