HARQ-ACK Codebook Segmentation for CBG and Fallback DCI
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently and flexibly handling variable HARQ-ACK bit reporting due to dynamic codebook determination, particularly in scenarios involving code block group (CBG) configurations and fallback downlink control information (DCI), leading to uncertainties in HARQ-ACK bit determination and payload size.
Innovation Solution
Implementing a hybrid approach with separate sub-codebooks for transport block (TB) and CBG-based HARQ-ACK reporting, using distinct DAI values, and dynamically adjusting HARQ-ACK bit reporting based on CBG configurations, with fallback DCI treated as regular DCI for consistent codebook size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate DAI processes are applied for TB based transmissions and CBG based transmissions with concatenated sub-codebooks, then the number of reported CBG HARQ-ACK bits per TB remains fixed, but the system cannot determine how many ACK bits should be reported for missed PDSCH when the number of HARQ-ACK bits per PDSCH is variable
Solution Approach 1:
The HARQ-ACK codebook is divided into multiple sub-codebooks, with each sub-codebook corresponding to a specific PDSCH reception. This segmentation allows the UE to independently determine the number of ACK bits for each sub-codebook based on the actual PDSCH reception status, resolving the ambiguity in bit determination while maintaining manageable complexity through modular structure
Solution Approach 2:
The codebook structure transitions from a fixed format to a dynamic format where the number of HARQ-ACK bits per PDSCH can vary. The UE determines the codebook size dynamically based on the actual number of PDSCH receptions and the configured HARQ-ACK bits per PDSCH, allowing adaptive adjustment without requiring complex separate DAI processes
2Stability of the object's composition
If TB-level HARQ-ACK is used for all PDSCHs within the association set when at least one PDSCH is scheduled by fallback DCI, then codebook size consistency is maintained, but flexibility in handling CBG-based transmissions is reduced
Solution Approach 1:
Different HARQ-ACK reporting modes are applied locally to different PDSCH transmissions based on their DCI type. PDSCHs scheduled by fallback DCI use TB-level HARQ-ACK, while PDSCHs scheduled by non-fallback DCI use CBG-level HARQ-ACK. This local differentiation maintains overall codebook consistency while providing flexibility for CBG-based transmissions where needed
Solution Approach 2:
The HARQ-ACK codebook is designed to universally handle both TB-level and CBG-level acknowledgments within a single unified structure. The codebook can accommodate mixed transmission types by integrating both TB-level and CBG-level HARQ-ACK bits, making the system versatile enough to handle various DCI formats and transmission modes without requiring separate codebooks
3Adaptability or versatility
If dynamic HARQ-ACK codebook is supported for CBG-based transmission, then reporting flexibility is improved, but the complexity of determining variable bit counts increases
Solution Approach 1:
The network pre-configures the UE with the number of HARQ-ACK bits to be reported per PDSCH through higher-layer signaling. This preliminary configuration allows the UE to quickly determine the codebook size without complex real-time calculations, reducing determination complexity while maintaining dynamic reporting flexibility for CBG-based transmissions
Data Source
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AI summary
A user equipment (UE) is described. The UE includes a processor and memory in electronic communication with the processor. Instructions stored in the memory are executable to receive a higher layer signalling to configure the UE with a code block group (CBG). The instructions are also executable to receive one or more downlink (DL) transmissions. Hybrid automatic repeat request acknowledgement (HARQ-ACK) of the one or more DL transmissions are multiplexed and reported in a single uplink (UL) reporting. The instructions are also executable to generate a HARQ-ACK codebook comprises a first HARQ-ACK sub-codebook and a second HARQ-ACK sub-codebook.