ACK/NACK Feedback Bit Determination for Multi-TDD Carrier Aggregation
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Solution Overview
Problem
In the LTE-A system, determining the number of ACK/NACK feedback bits for carriers with different TDD uplink/downlink configurations aggregated for a UE, especially when these carriers include both FDD and TDD carriers, is challenging, particularly when ACK/NACK is fed back over a PUSCH with a corresponding PDCCH including a DAI field, as existing solutions do not provide a specific method for such scenarios.
Innovation Solution
A method and apparatus that determine the number of ACK/NACK feedback bits by identifying a first category of carrier with a reference TDD uplink/downlink configuration indicating a set of indexes with more than 4 elements or a carrier with over 4 downlink subframes for ACK/NACK feedback, using a first category scheme if present, or obtaining the DAI value and minimum value from the reference TDD configuration if not, to calculate the number of downlink subframes and corresponding ACK/NACK feedback bits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple carriers with different TDD uplink/downlink configurations are aggregated for a UE, then the system peak data rate is improved, but the complexity of determining ACK/NACK feedback bits increases
Solution Approach 1:
The patent segments the determination of ACK/NACK feedback bits by categorizing carriers into different types (FDD carriers, TDD carriers with different uplink/downlink configurations). Each carrier type is handled with specific rules and formulas, breaking down the complex overall determination into manageable segments for each carrier type.
Solution Approach 2:
The patent changes parameters such as the number of downlink subframes M_c, the DAI value, and the uplink/downlink configuration indices to determine the appropriate number of ACK/NACK feedback bits. By dynamically adjusting these parameters based on carrier type and configuration, the system handles the complexity of multi-carrier aggregation while maintaining accurate feedback bit determination.
2Measurement precision
If a PUSCH with corresponding PDCCH including DAI field is used for ACK/NACK feedback, then the feedback accuracy is improved, but the difficulty of detecting and measuring the correct number of feedback bits increases
Solution Approach 1:
The patent uses the DAI field in the PDCCH as a feedback mechanism to indicate the number of downlink subframes. The DAI value provides explicit feedback information that helps the UE determine the correct number of ACK/NACK feedback bits, improving accuracy while reducing the difficulty of detection through standardized field interpretation.
Solution Approach 2:
The patent performs preliminary determination of the number of downlink subframes M_c and the DAI value before generating the ACK/NACK feedback. This preliminary action allows the system to pre-calculate the required number of feedback bits based on the PDCCH content and carrier configuration, making the actual feedback generation straightforward and accurate.
3Adaptability or versatility
If carriers with different TDD configurations are aggregated, then the system adaptability is improved, but the device complexity for handling various configuration scenarios increases
Solution Approach 1:
The patent creates a universal determination method that works across multiple carrier types (FDD and TDD) and various TDD uplink/downlink configurations (0-6). The same basic framework and formulas are applied universally, with specific parameters adjusted based on carrier type, providing adaptability without requiring separate complex handling for each scenario.
Data Source
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AI summary
A method and device for determining an ACK/NACK feedback bit number, used when a terminal groups carriers having different time division duplex (TDD) uplink/downlink configurations, and when the terminal conducts ACK/NACK feedback on a physical uplink sharing channel (PUSCH) having a corresponding physical downlink control channel (PDCCH), the PDCCH containing a downlink assignment index (DAI) domain. The method comprises: determining whether the carriers grouped by the terminal contain a first type carrier; if yes, then determining (I) of each carrier c according to a parameter indicating the number of ACK/NACK feedback subframes; if no, then acquiring (II) and the Mc of each carrier c, and selecting the minimum value from (II) and the Mc as the (I) of each carrier c; according to the number of the downlink subframes in each carrier c in need of conducting ACK/NACK feedback on the current uplink subframe, determining the ACK/NACK feedback bit number that the current uplink subframe needs to feed back. The present invention ensures normal operation of a system based on the application scenario.