Beam Failure Detection Using Mixed RLM Reference Signals
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in 5G NR systems is the need for accurate radio link monitoring (RLM) and beam-failure detection due to the ultra-lean design and extensive use of beamforming, which complicates the estimation of downlink quality using traditional methods like CRS, and requires efficient beam recovery mechanisms to maintain connectivity.
Innovation Solution
The proposed solution involves the UE performing RLM and beam-failure detection using a mix of multiple reference signals and physical channel quality indicators, including PDCCH, DMRS, and other RS types, to opportunistically measure downlink quality, even when not scheduled, thereby enhancing accuracy and reducing signaling overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional CRS-based RLM methods are used in 5G NR, then implementation simplicity is maintained, but measurement accuracy deteriorates due to ultra-lean design and beamforming
Solution Approach 1:
The patent combines multiple reference signal types (CSI-RS, SSB, DMRS) into a unified RLM measurement framework. The UE is configured to perform RLM measurements using a first reference signal type for initial quality assessment and a second reference signal type for confirmation, merging the strengths of different RS types to achieve accurate downlink quality estimation in beamformed 5G NR systems
Solution Approach 2:
The patent makes RLM measurement sources configurable and multi-functional. The same reference signal infrastructure (CSI-RS, SSB, DMRS) serves both beam management functions and RLM functions. The network can flexibly configure which RS type is used for RLM based on deployment scenarios, making the RLM mechanism universal across different 5G NR deployment types (standalone, non-standalone, frequency ranges)
2Measurement precision
If multiple reference signal types are used for RLM measurements, then measurement accuracy improves, but signaling overhead increases
Solution Approach 1:
The patent implements dynamic selection of reference signal types for RLM measurements. The UE is configured with multiple RS types but actively selects which ones to use based on current beam conditions, availability, and measurement requirements. This dynamic approach allows the system to use multiple RS types when needed for accuracy while falling back to single RS type or fewer measurements when conditions permit, thereby reducing overall signaling overhead
Solution Approach 2:
The patent changes the parameters of existing reference signals to serve dual purposes. By configuring CSI-RS, SSB, or DMRS with specific periodicities, bandwidths, and resource allocations optimized for both beam management and RLM, the system avoids introducing entirely new reference signals. This parameter optimization reduces the quantity of signaling required while maintaining measurement accuracy
3Productivity
If beamforming is extensively used in 5G NR, then spectral efficiency improves, but beam failure detection difficulty increases
Solution Approach 1:
The patent implements preliminary beam failure detection mechanisms by continuously monitoring reference signal quality before actual beam failure occurs. The UE performs RLM measurements on configured reference signals and compares against thresholds to detect deteriorating beam conditions early. This preliminary detection triggers beam recovery procedures before complete beam failure, enabling proactive beam management in extensively beamformed 5G NR systems while maintaining high spectral efficiency
Data Source
AI summary
A user equipment, UE, performs measurements based on a plurality of RLM sources received in beam-formed downlink signals, where the measurements indicate a quality of a given cell or beam. The plurality of sources comprises two or more of: first reference signals (RSs), second RSs of a different type than the first RSs, and one or more physical channel quality indicators obtained from non-reference-signal data in the beam-formed downlink signals. For each of the plurality of sources used to perform measurements, the UE determines whether a measurement for the respective source indicates an out-of-sync event in response to the measurement being below a first threshold. The UE then performs an RLM action based on determined occurrences of out-of-sync events.