L1/L2 Mobility for Secondary Cells in Carrier Aggregation
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Solution Overview
Problem
Current wireless communication systems face challenges in L1/L2 centric mobility, particularly for secondary cells, as existing specifications lack detailed procedures for inter-cell mobility and require RRC reconfiguration for SCell addition, modification, or release, leading to inefficiencies in handling multiple SCells in the same frequency and managing beam management.
Innovation Solution
Implement a method for L1/L2 mobility that allows the UE to change the secondary cell within the same frequency by receiving configurations and L1/L2 signaling, enabling the UE to switch between SCells without the need for RRC signaling, using TCI states and QCL sources to identify candidate cells and perform necessary state changes, such as deactivation or activation of SCells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RRC reconfiguration is used for SCell addition, modification, or release, then reliability of cell management is improved, but latency and signaling overhead increase
Solution Approach 1:
The patent segments the cell management process into two parts: RRC configuration for initial setup and L1/L2 signaling for dynamic changes. This allows RRC to handle reliable configuration while L1/L2 handles fast modifications, resolving the contradiction between reliability and latency.
Solution Approach 2:
The patent applies preliminary action by pre-configuring multiple SCells with RRC signaling before mobility is needed. When L1/L2 mobility signaling is received, the UE can immediately activate pre-configured SCells without waiting for RRC reconfiguration, thus reducing latency while maintaining reliability.
2Measurement precision
If RRC signaling is used for every SCell change, then measurement precision of cell state is improved, but device complexity increases
Solution Approach 1:
The patent divides signaling responsibilities between RRC (for configuration) and L1/L2 (for state changes). This segmentation reduces the complexity of L1/L2 signaling while maintaining accurate cell state management through the combination of both signaling layers.
Solution Approach 2:
The patent introduces L1/L2 signaling as an intermediary between RRC configuration and actual SCell activation. This intermediary allows the network to control SCell state changes efficiently without requiring complex RRC reconfiguration for every change, reducing overall signaling complexity.
3Productivity
If multiple SCells are configured in the same frequency, then network efficiency is improved, but difficulty of managing beam management increases
Solution Approach 1:
The patent applies universality by using a unified L1/L2 signaling mechanism (TCI state indication) that works for beam management across multiple SCells in the same frequency. This single mechanism handles beam management for all SCells, reducing the difficulty of managing multiple cells while maintaining network efficiency.
Data Source
AI summary
There is provided a method performed by a user equipment (UE) configured in Carrier Aggregation for handling Layer 1(L1)/Layer 2 (L2) mobility for secondary cells associated with a cell group, the UE being configured with a first cell as a secondary cell in a first frequency. The method may comprise: receiving a configuration of at least one second cell in the first frequency, wherein the at least one second cell is a candidate to become the secondary cell: receiving a L1/L2 signaling, which comprises an indication to change the secondary cell from the first cell to the second cell: and changing the secondary cell in the first frequency from the first cell to the second cell.