CU-DU DRB Change Signaling for Accurate L2 Handling
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Solution Overview
Problem
In the 5G CU-DU architecture, there is a challenge in ensuring that the DU accurately performs Layer 2 handling, particularly during bearer type changes or RLC failures, as the DU is not directly informed about the necessary configurations.
Innovation Solution
A notification method where the CU sends specific DRB identifiers and indication information to the DU, enabling the DU to perform accurate Layer 2 handling, including configurations such as MAC reset, RLC re-establishment, and bearer type changes, through messages like UE context modification requests over the F1 or W1 interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the CU-DU architecture is used to divide protocol layers independently, then the network flexibility and adaptability to various scenarios are improved, but the coordination complexity between CU and DU increases, making it difficult for the DU to learn about L2 handling requirements
Solution Approach 1:
The patent segments the notification process into distinct components: bearer identification information, indication information for L2 handling, and cell group configuration. This segmentation allows the CU to send targeted notifications to the DU without requiring complex full-state synchronization, thus maintaining network flexibility while reducing coordination complexity.
Solution Approach 2:
The patent introduces an intermediary notification mechanism where the CU sends specific indication information to the DU through defined interfaces (F1 or W1). This intermediary communication channel enables the DU to learn about L2 handling requirements without requiring direct complex coordination, resolving the contradiction between adaptability and coordination complexity.
2Extent of automation
If the DU is not directly informed about bearer type changes, then the CU maintains centralized control, but the DU cannot perform accurate Layer 2 handling configurations
Solution Approach 1:
The patent implements a feedback mechanism where the CU sends bearer identification information and indication information to the DU, enabling the DU to perform accurate L2 handling. The DU then sends response messages (UE Context Modification Response) back to the CU, confirming the configuration. This feedback loop maintains centralized control while ensuring configuration accuracy.
Solution Approach 2:
The patent applies preliminary action by having the CU send the indication information and cell group configuration to the DU before the DU performs the L2 handling. This allows the DU to be pre-informed about bearer type changes and prepare the appropriate configurations, ensuring both centralized control and configuration accuracy.
3Manufacturing precision
If detailed L2 handling information is transmitted from CU to DU, then the DU can perform accurate configurations, but the signaling overhead and message complexity increase
Solution Approach 1:
The patent extracts only the essential information needed for L2 handling from the full bearer context. Instead of transmitting complete bearer configurations, the CU sends specific bearer identification information and compact indication information (such as bearer type change indicators). This extraction maintains configuration accuracy while reducing signaling overhead.
Solution Approach 2:
The patent changes the parameter representation by using compact indication information (e.g., bearer type indicators, L2 handling type indicators) instead of transmitting full configuration parameters. This parameter transformation enables the DU to perform accurate L2 handling configurations while minimizing the amount of signaling data transmitted between CU and DU.
Data Source
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AI summary
Embodiments of this application provide a notification method, an apparatus, and a communications system, and relate to the communications field, to ensure that a DU performs accurate L2 handling in a CU-DU architecture. Specifically, the notification method includes: A CU sends a first message to the DU, where the first message includes an ID of a first DRB on which bearer type change occurs and first indication information indicating the DU to perform L2 handling; or the first message includes an ID of a first DRB and second indication information indicating that bearer type change occurs. The CU receives a second message sent by the DU, where the second message includes a cell group configuration of the L2 handling.