PDSCH Reception Switching via Layer 2 Mobility MAC CE
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Solution Overview
Problem
Current mobility mechanisms in 5G systems involve L3 measurements and RRC signaling, leading to increased latency, overhead, and interruption time during serving cell changes, which are not suitable for meeting the stringent requirements of future mobile communication systems.
Innovation Solution
Implementing layer 2 mobility by using MAC CEs to manage transitions between adjacent cells, allowing for seamless switching with reduced interruption through the use of data scrambling identities and TCI state lists for PDSCH reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If L3 measurements and RRC signaling are used for serving cell change, then mobility management is achieved, but latency and interruption time increase
Solution Approach 1:
The patent segments the mobility management process into two distinct layers: L1 beam switching for rapid beam selection and L2 MAC CE signaling for cell change confirmation. This segmentation allows the time-consuming L3 RRC signaling to be replaced with faster L2 MAC CE messages, reducing overall latency while maintaining reliable mobility management. The L1 layer handles rapid beam adjustments, while the L2 layer manages cell-level mobility, creating a hierarchical structure that optimizes both speed and reliability.
Solution Approach 2:
The patent implements preliminary action by pre-configuring multiple TCI states and data scrambling identities at the L2 layer before mobility is needed. When cell change is required, the UE can immediately switch to a pre-configured TCI state and scrambling identity without waiting for L3 RRC reconfiguration. This pre-preparation of mobility parameters significantly reduces interruption time while ensuring reliable cell transition.
2Reliability
If L3 measurements and RRC signaling are used for serving cell change, then cell transition is managed, but overhead increases
Solution Approach 1:
The patent extracts the essential cell transition management functions from the L3 RRC signaling layer and relocates them to the L2 MAC CE layer. By taking out the critical mobility management tasks (TCI state indication, scrambling identity assignment, cell change confirmation) and handling them at L2, the patent eliminates the need for extensive L3 RRC messages, thereby reducing signaling overhead while maintaining reliable cell transition management.
Solution Approach 2:
The patent uses copying by reusing existing L2 MAC CE structures and TCI state configurations for mobility management instead of creating new L3 RRC signaling mechanisms. The same MAC CE formats and TCI state representations used for beam management are copied and adapted for cell-level mobility, reducing overhead by leveraging existing L2 protocols rather than introducing new L3 signaling elements.
3Speed
If L1 switches between adjacent cells while layer 2 continues, then mobility speed increases, but coordination between layers becomes complex
Solution Approach 1:
The patent merges the L1 beam switching function with L2 cell change management by using the same MAC CE signaling structure for both beam indication and cell change confirmation. The TCI state indicators that traditionally only controlled beam selection are extended to also trigger cell changes when appropriate. This merging reduces the need for separate coordination mechanisms between L1 and L2, simplifying the overall layer coordination while maintaining high mobility switching speed.
Solution Approach 2:
The patent introduces the MAC CE as an intermediary layer between L1 beam switching and L2 cell management. The MAC CE serves as a mediator that translates L1 beam switching intentions into L2 cell change actions, and vice versa. This intermediary simplifies coordination by providing a standardized interface and message format that both layers can use, reducing the complexity of direct L1-L2 interaction while enabling fast mobility switching.
Data Source
AI summary
A method and apparatus for layer 2 mobility is provided. Method for lower layer mobility includes receiving from a base station a first RRC message, receiving from the base station a first MAC CE, the first MAC CE comprises an identifier related to the first data scrambling identity and the first TCI state list, performing PDSCH reception based on the first data scrambling identity and the first TCI state list, receiving from the base station a second MAC CE, the second MAC CE comprises an identifier related to the second data scrambling identity and the second TCI state list, and performing PDSCH reception based on the second data scrambling identity and the second TCI state list, The second MAC CE comprises an identifier related to the second data scrambling identity and a second TCI state list.