NR-U Radio Link Monitoring Evaluation Period Optimization
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Solution Overview
Problem
In New Radio Unlicensed (NR-U) systems, Radio Link Monitoring (RLM) evaluation periods for in-sync and out-of-sync detection are impacted by listen-before-talk (LBT) failures, leading to false alarms and increased latency, and the existing methods for optimizing RLM evaluation periods are not effective in balancing latency and accuracy for out-of-sync detection.
Innovation Solution
The proposed solution involves optimizing RLM evaluation periods by treating a skipped discovery reference signal (DRS) transmission due to LBT failure as a normal out-of-sync event, neglecting DRS mis-detection impacts, and compensating for measurement gain loss through proper scaling, and adapting reference signal time difference (RSTD) timing uncertainty based on sub-carrier spacing and reference resource element density to optimize positioning performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RLM evaluation period is extended to account for LBT failures, then detection accuracy improves, but latency increases
Solution Approach 1:
The patent changes the parameter of evaluation period duration based on the detection target. For out-of-sync detection, a longer evaluation period is used to account for LBT failures and avoid false alarms. For in-sync detection, a shorter evaluation period is used to reduce latency. This parameter adaptation resolves the contradiction by optimizing the evaluation period duration for different detection scenarios.
2Measurement precision
If DRS mis-detection is considered in RLM evaluation, then measurement accuracy improves, but system complexity increases
Solution Approach 1:
The patent extracts and separates the handling of DRS mis-detection from the main RLM evaluation process. By identifying specific conditions under which DRS transmissions may be skipped (e.g., LBT failures) and treating these as special cases, the patent simplifies the overall evaluation logic while maintaining accuracy. This extraction approach reduces complexity by avoiding the need to analyze every possible DRS detection scenario.
3Loss of time
If RLM evaluation is optimized for in-sync detection, then latency is reduced, but out-of-sync detection accuracy deteriorates
Solution Approach 1:
The patent applies different evaluation criteria and parameter settings for different detection targets (in-sync vs. out-of-sync). For in-sync detection, the evaluation is optimized for speed with shorter periods and different thresholds. For out-of-sync detection, the evaluation uses longer periods and adjusted thresholds to account for LBT failures. This local optimization of quality parameters for different functional requirements resolves the contradiction between latency and accuracy.
Data Source
AI summary
Various embodiments herein provide techniques for radio link monitoring (RLM) evaluation periods for in-sync and out-of-sync detection in new radio unlicensed (NR-U) spectrums. Additionally, embodiments provide techniques for reference signal time difference (RSTD) timing uncertainty configuration. Other embodiments may be described and claimed.