CU-DU RLF Report Segmentation for Beam Failure Recovery
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Solution Overview
Problem
The existing 5G RAN architecture faces challenges in efficiently handling radio link failures (RLFs) and beam failure recoveries due to misconfigurations in radio link monitoring (RLM), beam failure detection (BFD), and beam recovery (BFR) parameters, which lead to sub-optimal network performance and user experience.
Innovation Solution
The proposed solution involves a centralized unit (CU) that receives assistance information from user equipment (UE) for mobility robustness optimization (MRO), determines the failure cause and location, and forwards this information or necessary configuration changes to the appropriate distributed unit (DU) or second CU to address the root causes of RLFs and BFRs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gNB-CU handles RLF report forwarding centrally, then network control and optimization capability is improved, but communication latency and processing time increase
Solution Approach 1:
The patent segments the RLF handling functionality by introducing a new information element (IE) structure that separates gNB-CU generated RLF reports from gNB-DU generated RLF reports. This segmentation allows the gNB-CU to maintain centralized control for critical decisions while enabling the gNB-DU to handle local beam failure recovery operations independently, thus reducing communication latency for time-sensitive operations.
Solution Approach 2:
The patent introduces a new RLF-Report IE structure as an intermediary mechanism that carries both gNB-CU and gNB-DU RLF information through the F1 interface. This intermediary structure enables efficient information exchange between gNB-CU and gNB-DU, allowing the gNB-DU to provide beam failure recovery attempts information to the gNB-CU without requiring complex real-time communication protocols, thereby reducing processing time while maintaining centralized oversight.
2Speed
If the gNB-DU handles beam failure recovery locally, then response speed is improved, but network coordination and control precision decrease
Solution Approach 1:
The patent applies local quality by enabling the gNB-DU to independently handle beam failure recovery operations based on local beam quality measurements and configurations. The gNB-DU can autonomously initiate beam failure detection, declare beam failure, and attempt beam recovery using locally available candidate beams, providing fast local response without requiring continuous gNB-CU intervention for each beam failure event.
Solution Approach 2:
The patent implements a feedback mechanism where the gNB-DU reports beam failure recovery attempts and results to the gNB-CU through the new RLF-Report IE structure. This feedback loop allows the gNB-CU to maintain network-wide coordination and adjust beam failure recovery configurations based on reported performance, ensuring that local autonomous actions align with overall network optimization goals.
3Measurement precision
If detailed RLF assistance information is collected from UE, then diagnostic accuracy is improved, but information processing complexity increases
Solution Approach 1:
The patent extracts critical diagnostic information from detailed UE assistance information by defining a structured RLF-Report IE that selectively captures essential elements such as failure cause, serving cell identity, neighbor cell measurements, and beam failure recovery attempts. This extraction approach filters out redundant or less critical data, maintaining high diagnostic accuracy while reducing the complexity of information processing and storage in the gNB.
Data Source
AI summary
According to certain embodiments, a method is performed by a network node comprising a CU. The method comprises receiving assistance information for mobility robustness optimization and forwarding the assistance information, configuration changes related to mobility robustness optimization, or both to a DU or to a second CU. According to certain embodiments, a method is performed by a network node comprising a DU. The method comprises receiving assistance information for mobility robustness optimization. The assistance information indicates that a failure may have originated in a cell of the DU. The method further comprises performing one or more parameter changes in one or more functions handled by the DU.