Serving Cell Switching Fallback for RRC Reestablishment
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Solution Overview
Problem
Existing specifications for L1/L2-triggered mobility (LTM) in wireless communication systems lack methods for handling cell switch failures, particularly in terms of RRC connection recovery and security measures.
Innovation Solution
A terminal device and base station device implementation that includes a receptor for receiving cell change destination information and a controller for processing cell switching, with fail-safe mechanisms to maintain state variables and perform reestablishment procedures when initial switching fails, ensuring seamless cell transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If L1/L2-triggered mobility is implemented to reduce latency in mobility, then speed and capacity are improved, but reliability deteriorates due to lack of standardized recovery methods for RRC connection failures
Solution Approach 1:
The patent applies preliminary action by pre-configuring multiple cell change destination candidates before the actual cell switching occurs. The terminal device stores configuration information of candidate cells in advance, so when cell switching is triggered by L1/L2 signals, the terminal can immediately select from pre-prepared candidates without delay, thus maintaining high mobility speed while ensuring reliable RRC connection recovery through predetermined fallback options.
2Productivity
If cell switching is performed using Layer 1 and Layer 2 signals to reduce latency, then productivity is improved, but device complexity increases due to lack of standardized failure handling procedures
Solution Approach 1:
The patent applies segmentation by dividing the cell switching process into distinct phases: (1) receiving L1/L2 triggering signals for fast switching, (2) selecting from pre-configured cell change destination candidates, (3) executing cell switching to the selected candidate, and (4) performing RRC connection reestablishment only if necessary. This segmentation simplifies the failure handling procedure by clearly defining when and how to transition between different recovery mechanisms, reducing device complexity while maintaining high switching efficiency.
3Reliability
If standardized recovery methods are added for LTM failures, then reliability is improved, but device complexity increases due to additional processing procedures
Solution Approach 1:
The patent applies self-service by enabling the terminal device to autonomously determine the appropriate recovery mechanism based on the failure condition. When cell switching fails, the terminal automatically checks whether to perform RRC connection reestablishment or apply the second configuration from pre-stored cell change destination candidates. This self-service approach improves reliability through standardized recovery methods while minimizing processing complexity by eliminating the need for external intervention or complex decision-making algorithms.
Data Source
AI summary
A terminal device includes, a controller that performs first processing of switching a serving cell from a third cell to the first cell in accordance with the information related to the cell change, wherein the controller performs second processing including processing of maintaining some of values of state variables with a value of a first state variable and returning to a third configuration applied in the third cell to execute a reestablishment procedure when the first processing fails, the controller performs third processing of applying the second configuration applied in the second cell to switch the serving cell to the second cell in a case where the second cell is selected as a change destination cell and a first condition is satisfied in the second processing.