Uplink Synchronization in Carrier Aggregation Systems
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Solution Overview
Problem
Existing wireless access systems face challenges in acquiring uplink synchronization, particularly in Carrier Aggregation (CA) environments where multiple cells are aggregated, including the addition of geographically spaced Secondary Cells (SCells), which complicates the random access procedure and synchronization processes.
Innovation Solution
A method for acquiring uplink synchronization in a wireless access system supporting Carrier Aggregation (CA) involves receiving Random Access Channel (RACH) information from a Primary Cell (PCell) to perform a random access procedure with a Secondary Cell (SCell), including resource allocation and RACH parameter negotiation, enabling fast and efficient synchronization even with geographically spaced SCells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a random access procedure is performed with each SCell individually, then uplink synchronization can be acquired, but the synchronization time and complexity increase significantly
Solution Approach 1:
The invention performs preliminary actions by acquiring downlink synchronization with the SCell before the uplink random access procedure, and by preparing RACH information in advance through negotiation between the base station and SCell. This preliminary synchronization and preparation reduces the time required during the actual uplink synchronization process.
Solution Approach 2:
The invention merges the random access procedures by allowing the UE to perform a single random access procedure with the SCell that simultaneously achieves uplink synchronization for multiple aggregated cells. The base station coordinates this merged procedure by providing unified RACH information that covers resource allocation and parameters for the SCell group, reducing the number of separate procedures needed.
2Measurement precision
If RACH information is negotiated and configured for each SCell, then uplink synchronization accuracy improves, but the system complexity and signaling overhead increase
Solution Approach 1:
The invention makes the RACH information universal by creating a set of parameters that can be applied to multiple SCells simultaneously. The base station negotiates and configures a unified RACH configuration that serves as a common template for the SCell group, reducing the need for individual configurations while maintaining synchronization accuracy through cell-specific adjustments where necessary.
Solution Approach 2:
The invention segments the SCells into groups and assigns RACH information at the group level rather than individual cell level. This segmentation approach allows the system to manage complexity by handling SCells in manageable units while still providing precise synchronization control through group-specific RACH configurations.
3Reliability
If multiple random access procedures are performed for multiple SCells, then uplink synchronization is achieved, but the signaling overhead and processing load increase
Solution Approach 1:
The invention merges multiple random access procedures into a single coordinated procedure by having the base station provide unified RACH information that covers multiple SCells. The UE performs one random access procedure with the SCell, and the base station uses this procedure to establish synchronization for the aggregated cells, significantly reducing the signaling overhead compared to individual procedures for each SCell.
Data Source
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AI summary
The present invention provides a method used in a wireless access system supporting carrier aggregation (CA) for acquiring uplink synchronization from two or more geographically spaced cells, and a device for supporting the same. According to one embodiment of the present invention, a method for acquiring uplink synchronization in a wireless access system supporting CA can comprise the steps of: receiving, from a primacy cell (PCell), random access channel (RACH) information related to a first random access step for matching uplink synchronization in a secondary cell (SCell) to be added to CA; and performing the first random access step for matching uplink synchronization in the SCell on the basis of the RACH information.