Uplink Transmission Control for Secondary Cells in Carrier Aggregation
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Solution Overview
Problem
In carrier aggregation-based radio communication networks, when the time alignment timer of the primary cell group expires, secondary cell groups continue to send uplink transmissions, causing interference with other user equipment due to the lack of synchronization, as the time alignment timer operates only based on the primary cell group.
Innovation Solution
The method involves terminating uplink transmission over activated secondary cells in the secondary cell group when the primary cell's time alignment timer expires, and transmitting specific messages (RRC or MAC CE) to deconfigure or deactivate secondary cells, ensuring synchronization is maintained and interference is avoided.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single time alignment timer is shared by both primary cell group and secondary cell group, then device complexity is reduced, but reliability deteriorates because the timer cannot independently track synchronization status of secondary cells
Solution Approach 1:
The patent divides the time alignment timer into separate timers for primary cell group (TAT_PCG) and secondary cell group (TAT_SCG). This segmentation allows each timer to independently track synchronization status, resolving the contradiction by maintaining simplicity through separate timer management while improving reliability through independent tracking capability.
2Reliability
If separate time alignment timers are configured for primary cell group and secondary cell group, then reliability of time alignment tracking is improved, but device complexity increases
Solution Approach 1:
The patent implements separate time alignment timers (TAT_PCG and TAT_SCG) for primary and secondary cell groups, which improves reliability by enabling independent tracking of synchronization status. The complexity is managed through structured configuration where each timer operates independently with well-defined activation and deactivation conditions.
3Productivity
If uplink transmission continues on secondary cells after primary cell time alignment expires, then productivity is maintained, but harmful factors increase due to interference with other user equipments
Solution Approach 1:
The patent applies preliminary action by deactivating secondary cells before the harmful interference occurs. When TAT_PCG expires, the system immediately deactivates secondary cells in advance, preventing uplink transmissions that would cause interference. This resolves the contradiction by proactively stopping transmission rather than allowing it to continue and cause harm.
Solution Approach 2:
The patent converts the harmful effect of continued uplink transmission into a beneficial action by using the TAT_SCG timer to control deactivation. The timer mechanism, which could have been seen as adding complexity, actually provides a clean solution by automatically managing cell deactivation based on synchronization status, turning potential harm into controlled, beneficial termination of transmissions.
Data Source
AI summary
The invention proposes a method, in a carrier aggregation transmission-based radio communication network, of controlling uplink transmission of a user equipment over a plurality of secondary cells in a group of secondary cells, the user equipment being configured with a group of primary cells and at least one group of secondary cells, and the group of secondary cells belonging to the at least one group of secondary cells, wherein in the event that the group of primary cells and the at least one group of secondary cells each is configured with a time alignment timer, the method comprises the steps of: terminating the uplink transmission of the user equipment over at least one activated secondary cell in the group of secondary cells when the time alignment timer of the group of primary cells expires; in the event that the group of primary cells and the at least one group of secondary cells are configured with a common time alignment timer, the method comprises the steps of: determining whether a time alignment value of the group of secondary cells is valid when the time alignment timer is in operation; and if not, terminating the uplink transmission of the user equipment over the at least one activated secondary cell in the group of secondary cells and transmitting a notification message to a base station.