Independent Synchronization Timers for Carrier Aggregation Resynchronization
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Solution Overview
Problem
In LTE radio communication systems, the expiration of a synchronization timer in one cell group leads to a significant delay in resynchronization of other cell groups, resulting in reduced throughput due to sequential resynchronization processes across multiple cell groups during carrier aggregation.
Innovation Solution
Implementing independent synchronization timers for each cell group, allowing the second synchronization timer to continue running even after the first timer expires, enabling immediate uplink signal transmission on secondary cell groups once resynchronization is established on the primary cell group.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single synchronization timer is used for all cell groups, then control complexity is reduced, but resynchronization delay increases when multiple cell groups need simultaneous resynchronization
Solution Approach 1:
The patent divides the synchronization timer into multiple independent timers, with each timer corresponding to a specific cell group. This segmentation allows each cell group to be resynchronized independently, eliminating the sequential dependency that causes delay when multiple cell groups need resynchronization. The timer indicator field in DCI messages enables the base station to selectively activate or deactivate specific timers for different cell groups, achieving parallel resynchronization without significantly increasing overall control complexity.
2Ease of operation
If sequential resynchronization is performed across multiple cell groups, then control simplicity is maintained, but throughput decreases due to waiting delays
Solution Approach 1:
The patent introduces dynamic timer management where the base station can independently control the state (running or stopped) of each synchronization timer based on the resynchronization needs of different cell groups. The timer indicator field in DCI messages provides dynamic control, allowing the base station to start, stop, or restart specific timers as needed. This dynamic approach enables parallel resynchronization operations across multiple cell groups, significantly improving throughput while maintaining reasonable control simplicity through standardized signaling mechanisms.
3Device complexity
If the synchronization timer is stopped for all cell groups when one timer expires, then timing control is simplified, but resynchronization efficiency of other cell groups deteriorates
Solution Approach 1:
The patent segments the synchronization timer into multiple independent timers, each dedicated to a specific cell group. When one timer expires, only the corresponding cell group is affected, while other cell groups continue their normal operation with their own running timers. This segmentation eliminates the cascading effect where one expiration stops all other cell groups, thereby maintaining resynchronization efficiency across the system.
Solution Approach 2:
The patent applies local quality by allowing different synchronization states for different cell groups. Each cell group can have its own timer state (running or stopped) independent of others, enabling localized resynchronization control. The base station can selectively manage timer states based on the specific needs of each cell group, optimizing resynchronization efficiency without requiring system-wide timer coordination.
Data Source
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AI summary
A radio station, a radio terminal, and a method for synchronization timer control are provided that can reduce a delay as much as possible until uplink signal resynchronization is done in a case where a plurality of cell groups exist. In a radio communication system having a function of using a plurality of radio resources corresponding to a plurality of cells, respectively, for communication between a radio station (10) and a radio terminal (20), the radio terminal is provided with a plurality of synchronization timers for determining whether or not uplink signals in individual cell groups are in synchronization, wherein the synchronization timers are provided respectively for the plurality of cell groups each including at least one cell, and at the radio terminal (20), uplink-signal transmission on the cells included in a second cell group is controlled depending on a state of a first synchronization timer provided correspondingly for a first cell group including a specific cell and on a state of a second synchronization timer provided correspondingly for the second cell group other than the first cell group, wherein the first synchronization timer and the second synchronization timer are controlled independently.