HARQ-ACK Transmission in Carrier Aggregation with Variable DAI
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Solution Overview
Problem
In carrier aggregation-based wireless communication systems, there is a challenge in efficiently transmitting and receiving control information and acknowledgement information on downlink/uplink signals, particularly due to differences in subframe configurations between cells.
Innovation Solution
The method involves configuring a first cell and a second cell with different subframe configurations, using a downlink control information format that includes a downlink assignment index field, and transmitting hybrid automatic repeat request (HARQ)-acknowledgement information, where the use of the downlink assignment index field varies based on the reference uplink-downlink configuration applied to the second cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different subframe configurations are applied to multiple cells in carrier aggregation, then system flexibility and adaptability are improved, but control information transmission complexity increases
Solution Approach 1:
The patent segments the control information transmission by introducing a Cell-specific Downlink Assignment Index (Cell-DAI) for each cell and a Total Downlink Assignment Index (Total-DAI) across all cells. This segmentation allows each cell to be independently configured with different subframe configurations while maintaining overall system coordination through the Total-DAI mechanism.
Solution Approach 2:
The patent applies local quality by allowing each cell to have its own Downlink Assignment Index (DAI) configuration tailored to its specific subframe pattern. The Cell-DAI is independently configured per cell based on its local subframe configuration, enabling optimized control information transmission for each cell's specific characteristics.
2Measurement precision
If Downlink Assignment Index field is always used for HARQ-ACK timing, then acknowledgment accuracy is improved, but signaling overhead increases
Solution Approach 1:
The patent introduces dynamic adaptability by making the use of Downlink Assignment Index (DAI) fields optional rather than mandatory. The system can dynamically switch between using Cell-DAI/Total-DAI mechanisms and alternative HARQ-ACK timing determination methods based on the specific subframe configuration and operational requirements, thereby reducing signaling overhead when full DAI functionality is not needed.
Solution Approach 2:
The patent changes the parameter of DAI field usage from a fixed state (always used) to a variable state (conditionally used). By introducing configuration parameters that control whether Cell-DAI and Total-DAI are enabled, the system can adjust the level of DAI functionality based on network conditions and requirements, optimizing the balance between timing accuracy and signaling overhead.
Data Source
AI summary
The present invention relates to a wireless communication system, particularly, a method in which a terminal transmits control information in a CA-based wireless communication system and an apparatus for the method, the method comprising: configuring a first cell and a second cell having different subframe configurations, wherein the second cell has any one of UL-DL configuration #0 to #6; receiving a DC) format including a DAI field, for the second cell; and transmitting HARQ-ACK information relating to the downlink DCI format. For HARQ-ACK timing, in cases where a reference UL-DL configuration applied to the second cell is any one of UL-DL configurations #1 to #6, the DAI field is used in a process of transmitting the HARQ-ACK information. For HARQ-ACK timing, in cases where a reference UL-DL configuration applied to the second cell is #0, the DAI field is not used in a process of transmitting the HARQ-ACK information.