Uplink Timing Control for Wireless Carrier Aggregation
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Solution Overview
Problem
In wireless communication systems supporting Carrier Aggregation (CA), there is a need for efficient control of cell activation, particularly in managing uplink transmission timing to prevent interference and ensure proper synchronization across multiple cells.
Innovation Solution
A method and apparatus where a User Equipment (UE) receives a signal with Timing Advance Group (TAG) information, considering a Secondary Cell (SCell) as having no valid uplink timing if the Time Alignment Timer (TAT) is not running, leading to the flushing of Hybrid ARQ Repeat reQuest (HARQ) buffers, releasing Physical Uplink Control Channel (PUCCH) resources, and clearing downlink and uplink grants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a Secondary Cell (SCell) is activated in a wireless communication system supporting Carrier Aggregation, then the system capacity and data rate are improved, but uplink timing misalignment and interference may occur if the Time Alignment Timer (TAT) is not properly managed
Solution Approach 1:
The patent applies preliminary action by checking whether the Time Alignment Timer (TAT) is running before activating a Secondary Cell (SCell). The UE determines if the SCell has valid uplink timing in advance by checking if TAT is running, and only activates the SCell if timing is valid. This prevents timing misalignment and interference before they can occur, resolving the contradiction between improving system capacity through SCell activation and maintaining uplink timing alignment reliability.
2Reliability
If the Time Alignment Timer (TAT) is not running for a Timing Advance Group (TAG), then interference is prevented by avoiding uplink transmission, but the cell activation efficiency and resource utilization are reduced
Solution Approach 1:
The patent applies dynamics by making the SCell activation decision conditional and dynamic based on the real-time state of the Time Alignment Timer (TAT). Rather than a static approach of always allowing or disallowing SCell activation, the system dynamically checks whether TAT is running and adjusts the activation decision accordingly. This dynamic adaptation resolves the contradiction by enabling SCell activation only when timing is valid (maintaining reliability) while allowing activation when timing is valid (improving productivity).
Solution Approach 2:
The patent applies self-service by enabling the UE to autonomously determine whether an SCell has valid uplink timing by checking if the TAT is running, without requiring explicit network signaling for each activation decision. The UE independently evaluates the timing validity and makes the activation decision, improving cell activation efficiency while maintaining interference prevention through the TAT mechanism.
3Adaptability or versatility
If multiple Timing Advance Groups (TAGs) are configured for carrier aggregation, then the flexibility and adaptability of uplink timing control are improved, but the complexity of timing management and synchronization increases
Solution Approach 1:
The patent applies segmentation by dividing the uplink timing management into separate Timing Advance Groups (TAGs), where each TAG can be independently managed with its own TAT. The UE checks the TAT status for each TAG independently when determining SCell activation, allowing flexible and independent timing control for different cell groups. This segmentation resolves the contradiction by providing adaptability through independent TAG management while reducing complexity through modular, independent TAT checking for each TAG.
Data Source
AI summary
The present invention is directed to a method and an apparatus used for in a wireless communication system. Specifically, the present invention is directed to a method of controlling uplink transmission and an apparatus therefore, in which the method comprises: receiving a signal including information related with an assignment of a TAG for SCell; and considering SCell as having no valid uplink timing if TAT of the TAG is not running.