HARQ-ACK Codebook Size Determination in LTE Carrier Aggregation
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Solution Overview
Problem
In wireless communication networks, especially in LTE systems with interband carrier aggregation, the existing methods for determining the HARQ-ACK codebook size fail to effectively reduce HARQ-ACK overhead while maintaining performance, particularly in scenarios with different UL-DL configurations for different serving cells.
Innovation Solution
The proposed solution involves a method for user equipment (UE) to adaptively determine the HARQ-ACK codebook size by calculating the number of HARQ-ACK bits based on the downlink assignment index (DAI) and the number of subframes within the bundling window for each serving cell, using specific equations to minimize overhead and optimize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the HARQ-ACK codebook size is determined by the maximum bundling window size across all serving cells, then all downlink subframes are covered, but HARQ-ACK overhead increases significantly
Solution Approach 1:
The patent segments the HARQ-ACK codebook determination by serving cell, calculating the bundling window size separately for each serving cell based on its specific UL-DL configuration. This allows the UE to determine the codebook size per serving cell rather than using a single maximum value for all serving cells, thereby reducing overall HARQ-ACK overhead while maintaining reliable coverage for each individual serving cell.
2Quantity of substance
If the bundling window size is reduced to match actual scheduled subframes, then HARQ-ACK overhead is reduced, but some downlink subframes may not be covered
Solution Approach 1:
The patent implements dynamic adaptation of the bundling window size for each serving cell based on its specific UL-DL configuration and actual downlink scheduling. The UE determines the bundling window size dynamically rather than using a fixed maximum value, allowing the system to adapt to actual scheduling conditions while ensuring all scheduled downlink subframes are covered. This dynamic approach reduces HARQ-ACK overhead by avoiding allocation of bits for unscheduled subframes.
3Adaptability or versatility
If different UL-DL configurations are used for different serving cells, then system flexibility and adaptability improve, but HARQ-ACK codebook determination becomes complex
Solution Approach 1:
The patent applies local quality by determining the bundling window size independently for each serving cell based on its specific UL-DL configuration. Each serving cell's HARQ-ACK codebook is optimized locally according to its own configuration characteristics rather than applying a uniform approach. This allows the system to maintain high adaptability with different UL-DL configurations while managing complexity through localized, independent determination for each serving cell.
Data Source
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AI summary
Embodiments of the present disclosure describe devices, methods, computer-readable media and systems configurations for determining a hybrid automatic repeat request (HARQ)-acknowledgment (ACK) codebook in wireless communication networks.