CU-DU Interworking for Low-Latency L1/L2 Cell Switching
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Solution Overview
Problem
Current methods for serving cell changes in cellular networks involve layer 3 (L3) measurements and radio resource control (RRC) signaling, leading to longer latency, larger overhead, and longer interruption times during mobility events.
Innovation Solution
Implementing lower-layer signaling (L1/L2) for cell changes, with mechanisms for CU-DU interface signaling to support L1/L2 based mobility, including configuration and management of candidate cells, dynamic switch mechanisms, and beam management, to reduce latency and overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If L3 measurements and RRC signaling are used for serving cell changes, then reliability is ensured through complete L2 and L1 resets, but latency and interruption time increase
Solution Approach 1:
The patent segments the mobility procedure into separate phases: L1/L2 preparation and configuration phases are separated from the actual cell switch execution. This allows the network to prepare candidate cells and configure L1/L2 parameters in advance, then execute the cell switch rapidly when needed, reducing overall latency while maintaining reliability through the structured multi-phase approach
Solution Approach 2:
The patent implements preliminary actions by configuring L1/L2 parameters and preparing candidate cells before the actual serving cell change is needed. The network pre-configures multiple candidate cells with their L1/L2 settings, so when a cell change is required, the UE can switch immediately without waiting for complete L2/L1 reset procedures, thus reducing mobility latency while ensuring reliability
2Reliability
If L3 measurements and RRC signaling are used for serving cell changes, then complete L2 and L1 resets ensure proper synchronization, but overhead increases
Solution Approach 1:
The patent extracts the L1/L2 configuration and preparation steps from the traditional L3 RRC signaling flow. By separating L1/L2 signaling from L3 RRC procedures, the patent reduces RRC signaling overhead while maintaining reliability through dedicated L1/L2 configuration messages that are more efficient and can be processed faster than complete L2/L1 reset sequences
Solution Approach 2:
The patent introduces an intermediary L1/L2 signaling layer that mediates between the RRC layer and the physical layer during cell changes. This intermediary signaling mechanism allows for more efficient cell switch coordination without requiring complete L2/L1 resets, reducing overhead while ensuring proper synchronization and reliability through the intermediate configuration step
3Loss of time
If L1/L2 based mobility is implemented, then latency and overhead are reduced, but CU-DU interface signaling needs to be further developed
Solution Approach 1:
The patent implements dynamic CU-DU interface signaling that adapts to different mobility scenarios. The interface signaling is designed to be flexible and configurable, allowing the network to optimize the balance between latency reduction and interface complexity based on specific deployment requirements and mobility patterns, rather than requiring fixed complex procedures for all cases
Data Source
AI summary
Embodiments of the present disclosure relate to methods, devices and computer readable media for communication. A source DU transmits, to a CU, first information regarding at least one candidate cell for a lower-layer signaling based cell change or addition; and receives, from the CU, second information regarding a target cell for the lower-layer signaling based cell change or addition. In this way, CU-DU interworking for L1/L2 based mobility may be defined.