Uplink Synchronization for Carrier Aggregation Secondary Cells
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Solution Overview
Problem
In wireless access systems supporting carrier aggregation (CA), acquiring uplink synchronization with secondary cells (Scells) added in a CA environment, especially those geographically spaced apart, is challenging, leading to potential errors in operation when a cell is mistakenly identified as a primary cell.
Innovation Solution
A method for acquiring uplink synchronization from multiple geographically spaced S-cells and indicating S-cell status to prevent errors, involving a random access procedure where the user equipment (UE) performs a RACH procedure with S-cells using pre-acquired RACH information and transmits S-cell indication messages to ensure correct configuration in the CA environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a random access procedure is performed with newly added S-cells in CA environment, then uplink synchronization can be acquired, but the complexity of the procedure increases due to geographic spacing and potential identification errors
Solution Approach 1:
The patent applies preliminary action by pre-configuring RACH information for S-cells before the actual random access procedure. The eNB prepares and transmits RACH configuration information to the UE in advance, so that when the UE needs to access an S-cell, the necessary parameters are already available, reducing the complexity of real-time configuration and ensuring reliable synchronization acquisition.
Solution Approach 2:
The patent uses S-cell indication information as an intermediary mechanism to distinguish between P-cells and S-cells. This indication flag acts as a mediator that prevents the UE from mistakenly treating an S-cell as a P-cell, thereby avoiding identification errors and ensuring correct procedure execution while maintaining reliable synchronization.
2Reliability
If S-cell indication information is transmitted to prevent error operation, then reliability improves, but the amount of control information increases
Solution Approach 1:
The patent applies local quality by adding S-cell indication information only to the specific control messages related to S-cell configuration, rather than redesigning the entire control information structure. This targeted approach minimizes the increase in control information overhead while ensuring reliable cell identification where it is most needed.
Data Source
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AI summary
The present invention, which is utilized in a wireless access system supporting carrier aggregation (CA), relates to methods for acquiring an uplink synchronization from two or more geographically distanced cells, particularly S-cells, and indicating that the corresponding cell is an S-cell, and to an apparatus for supporting same.