HARQ-ACK Timing in TDD Carrier Aggregation
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Solution Overview
Problem
In a Carrier Aggregation (CA) system, the flexible change in distribution of UpLink/DownLink (UL/DL) sub frames poses challenges for correctly determining the timing of Hybrid Automatic Repeat reQuest ACKnowledgement (HARQ-ACK) transmission, affecting both base stations and User Equipment (UE) in correctly sending and receiving HARQ-ACK for proper downlink HARQ transmission.
Innovation Solution
A method and apparatus for transmitting HARQ-ACK in a Time Division Duplexing (TDD) CA system, where the duplex direction of sub frames changes flexibly, involve determining the distribution of fixed and flexible sub-frames, using reference UL/DL configurations to establish HARQ-ACK timing, and transmitting HARQ-ACK based on these determinations, without introducing new timing schemes, thereby ensuring correct HARQ-ACK transmission without impacting downlink scheduling flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If flexible sub-frame distribution is implemented to adapt to varying service demands, then adaptability is improved, but HARQ-ACK timing determination becomes complex and error-prone
Solution Approach 1:
The patent introduces a reference UL/DL configuration as an intermediary that mediates between the actual flexible sub-frame distribution and the HARQ-ACK timing determination. The reference configuration serves as a stable basis for timing calculation, while the actual configuration can flexibly adapt to service demands. This intermediary layer allows the system to maintain adaptability without directly coupling the complexity of flexible configuration changes to the HARQ-ACK timing mechanism.
Solution Approach 2:
The patent changes the parameter of UL/DL configuration from fixed to flexible by allowing dynamic adjustment of sub-frame directions. However, it maintains HARQ-ACK timing determination by referencing a stable configuration parameter, thus achieving parameter flexibility without compromising timing accuracy.
2Measurement precision
If reference UL/DL configuration is used to determine HARQ-ACK timing, then timing determination accuracy is improved, but flexibility in downlink scheduling is reduced
Solution Approach 1:
The patent segments the UL/DL configuration into two parts: a reference configuration used for HARQ-ACK timing determination and an actual configuration used for downlink scheduling. This segmentation allows the reference configuration to provide accurate timing determination while the actual configuration maintains scheduling flexibility, resolving the contradiction between precision and adaptability.
Solution Approach 2:
The patent makes the system dynamic by allowing the actual UL/DL configuration to change flexibly for scheduling purposes while the reference configuration remains stable for timing determination. This dynamic approach enables the system to adapt to varying service demands without compromising HARQ-ACK timing accuracy.
3Device complexity
If conventional HARQ-ACK timing schemes are reused, then system complexity is reduced, but compatibility with flexible sub-frame distribution is limited
Solution Approach 1:
The patent makes the conventional HARQ-ACK timing schemes universal by introducing a reference UL/DL configuration that can represent any flexible sub-frame distribution pattern. The reference configuration serves multiple functions: it maintains compatibility with existing timing schemes while adapting to flexible distribution requirements, thus achieving multi-functionality without increasing system complexity.
Data Source
Figure 1~3
AI summary
An apparatus and a method are provided for transmitting a Hybrid Automatic Repeat reQuest ACKnowledgement (HARQ-ACK) in a Time Division Duplexing (TDD) Carrier Aggregation (CA) system, wherein the duplex direction of a sub frame may change flexibly. According to the method, a UE receives configuration information from a base station for each cell working under a CA mode; determines a distribution of fixed sub frames and flexible sub frames in each cell; determines timing of a HARQ-ACK for downlink transmission in each cell; and transmits the HARQ-ACK, based on the determined timing of the HARQ-ACK for each cell.