HARQ-ACK Codebook Indexing for Multi-TTI PDSCH Scheduling
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Solution Overview
Problem
In wireless communication networks, the high blind detection overhead of downlink control information (DCI) is exacerbated by multi-TTI PDSCH scheduling, leading to increased complexity and uncertainty in hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback, particularly when multiple PDSCHs are scheduled by a single piece of DCI.
Innovation Solution
A method for determining HARQ-ACK codebooks by user equipment (UE) and network devices, where index parameters like C-DAI and T-DAI are adjusted based on the number of scheduled DCIs, maintaining the original bit occupancy to accurately generate type-2 HARQ-ACK codebooks, ensuring coordination and consistency between UE and network devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multi-TTI PDSCH scheduling is used to reduce DCI overhead, then the number of DCI pieces is reduced, but the complexity of HARQ-ACK feedback increases due to multiple PDSCHs scheduled by a single DCI
Solution Approach 1:
The patent segments the HARQ-ACK feedback process by introducing separate index parameters (first index parameter for counting DCIs, second index parameter for indicating PDSCH position) to independently track DCI数量 and PDSCH scheduling information. This segmentation allows the system to handle multiple PDSCHs scheduled by a single DCI without increasing overall feedback complexity, as each parameter handles a specific aspect of the scheduling information.
Solution Approach 2:
The patent introduces index parameters as intermediary elements between the DCI and HARQ-ACK feedback. These index parameters (particularly the second index parameter) act as mediators that carry scheduling information from the DCI to the HARQ-ACK codebook construction process, enabling the system to resolve the complexity issue by providing structured intermediate representation of the scheduling relationships.
2Measurement precision
If the number of bits for index parameters is increased to accurately indicate multiple PDSCHs, then HARQ-ACK feedback accuracy improves, but DCI overhead increases
Solution Approach 1:
The patent applies partial action by using the second index parameter only when multi-TTI scheduling is detected (based on the relationship between scheduling time and PDSCH time). When single-TTI scheduling is used, the full precision of indicating all PDSCHs is not needed, thus avoiding unnecessary bit overhead. The system provides precise indication only when required by the scheduling scenario.
Solution Approach 2:
The patent changes the parameter structure by introducing a conditional second index parameter that is only activated when multi-TTI scheduling is detected. This parameter change allows the system to maintain accurate HARQ-ACK feedback for multi-TTI scenarios while avoiding the bit overhead that would result from always including comprehensive PDSCH position indication parameters in all DCIs.
3Adaptability or versatility
If each PDSCH is scheduled with one piece of DCI individually, then scheduling flexibility is maintained, but blind detection overhead of DCI becomes too high
Solution Approach 1:
The patent merges multiple PDSCH scheduling operations into a single DCI structure by introducing a second index parameter that can indicate multiple PDSCH positions. This merging reduces the number of separate DCI messages needed, thereby reducing blind detection overhead, while the index parameter structure preserves the ability to individually address and acknowledge each scheduled PDSCH, maintaining scheduling flexibility.
4Device complexity
If one piece of DCI schedules multiple PDSCHs, then DCI detection complexity is reduced, but uncertainty in HARQ-ACK feedback increases
Solution Approach 1:
The patent implements feedback mechanisms where the second index parameter in the DCI provides explicit information about the number and position of scheduled PDSCHs. This feedback information allows the UE to accurately construct the HARQ-ACK codebook with the correct number of acknowledgment bits for each scheduled PDSCH, eliminating uncertainty. The network can verify the correct interpretation of the scheduling by comparing the second index parameter values with the actual PDSCH transmissions.
Data Source
AI summary
A method for determining a hybrid automatic repeat request acknowledgement (HARQ-ACK) codebook, performed by a user equipment, including: determining an index parameter according to a number of at least one piece of downlink control information (DCI), in response to a network device scheduling the at least one piece of DCI, and each piece of DCI in the at least one piece of DCI scheduling at least one physical downlink shared channel (PDSCH); and determining the HARQ-ACK codebook corresponding to the at least one piece of DCI according to the index parameter and a value that is less than a maximum number of PDSCHs schedulable by a single piece of DCI. The maximum number of PDSCHs schedulable by the single piece of DCI is semi-statically configured by a high layer signaling or specified in a protocol.