Dynamic HARQ-ACK Codebook Adjustment for Carrier Aggregation
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Solution Overview
Problem
In existing LTE systems, the bit size of ACKs/NACKs is semi-statically determined and fixed based on the number of component carriers, leading to inefficient overhead and potential communication quality deterioration when the number of scheduled carriers differs from the configured carriers, especially with the expansion to more than five carriers in later versions.
Innovation Solution
A user terminal with a receiving section for downlink signals and a control section that adjusts HARQ-ACK transmission based on a counter DAI included in downlink control information, configured with three or more bits, allowing dynamic adjustment of the codebook size according to the number of scheduled carriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the codebook size is semi-statically determined based on the number of configured component carriers, then the user terminal can prepare for maximum carrier aggregation, but the overhead increases when fewer carriers are actually scheduled
Solution Approach 1:
The patent applies dynamics by transitioning from a semi-static codebook size determination to a dynamic one. The codebook size is now determined based on the actual number of scheduled component carriers rather than the maximum configured number. This allows the HARQ-ACK feedback size to adapt dynamically to the actual scheduling needs, reducing overhead when fewer carriers are scheduled while maintaining the ability to handle up to 8 carriers when all are scheduled.
2Device complexity
If the codebook size is fixed based on the number of component carriers, then the feedback mechanism is simple, but communication quality deteriorates when the number of scheduled carriers differs from configured carriers
Solution Approach 1:
The patent applies parameter changes by modifying the codebook size parameter dynamically. Instead of using a fixed codebook size determined by the number of configured carriers, the system changes the codebook size parameter based on the actual number of scheduled carriers. This parameter adjustment ensures that the HARQ-ACK feedback matches the actual scheduling situation, preventing communication quality deterioration while maintaining manageable mechanism complexity.
3Productivity
If the number of component carriers is increased beyond five, then the bandwidth and data rate improve, but the existing HARQ-ACK feedback mechanism becomes insufficient
Solution Approach 1:
The patent applies dynamics by enabling the HARQ-ACK feedback mechanism to adapt to an increased number of component carriers. The codebook size is dynamically determined based on the actual number of scheduled carriers, allowing the system to support up to 8 carriers. This dynamic adjustment maintains the feedback mechanism's versatility and capability as the system scales to higher data rates with more carriers.
Data Source
AI summary
The present invention is designed so that it is possible to feed back HARQ-ACKs adequately even when a plurality of component carriers are configured in a radio communication system. The present invention provides a receiving section that receives DL signals transmitted from a plurality of component carriers (CCs), and a control section that controls transmission of an HARQ-ACK in response to a received DL signal based on a counter DAI included in the downlink control information, and the counter DAI is configured to three or more bits in predetermined downlink control information. Also, the counter DAI can be comprised of varying numbers of bits depending on the number of CCs configured in the user terminal or the number of CCs where listening is applied to DL transmission.