HARQ-ACK Codebook Determination via DAI Fields
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wireless communication systems, particularly in 5G NR and LTE, there is a need to efficiently handle hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback determination to avoid misunderstandings between user equipment (UE) and base stations, which can lead to retransmissions and degradation of downlink performance due to incorrect HARQ-ACK codebook generation.
Innovation Solution
A carrier-domain HARQ-ACK bundling scheme is employed, where DCI formats include counter and total DAI fields to indicate PDCCH receptions, allowing UEs to generate accurate HARQ-ACK codebooks even when some DCI formats are missed, ensuring synchronized understanding between UEs and base stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HARQ-ACK codebook is generated without proper indication information for multi-carrier scheduling, then device complexity is reduced, but misunderstandings between UE and base station occur leading to retransmissions and performance degradation
Solution Approach 1:
The DCI format is segmented to include separate indication fields: counter DAI information indicating the order of PDCCH receptions, and total DAI information indicating the total number of PDCCH receptions. This segmentation allows the UE to accurately determine HARQ-ACK codebook structure without requiring complex cross-carrier scheduling logic, thus improving reliability while maintaining manageable complexity.
Solution Approach 2:
The counter DAI and total DAI fields act as intermediaries between the base station's scheduling decisions and the UE's HARQ-ACK codebook generation. These indication fields carry essential ordering and counting information that mediates the synchronization between transmitter and receiver, eliminating misunderstandings without requiring complex direct interpretation of scheduling patterns.
2Adaptability or versatility
If multiple DCI formats are used for scheduling PDSCH on multiple serving cells, then scheduling flexibility is improved, but the risk of missing DCI formats and generating incorrect codebooks increases
Solution Approach 1:
The base station performs preliminary action by embedding counter DAI and total DAI information in each DCI format before transmission. This pre-packaging of ordering and counting information ensures that even if the UE misses some DCI formats, it can still accurately reconstruct the HARQ-ACK codebook structure using the indication information from received DCI formats, thus maintaining reliability while preserving scheduling flexibility.
Solution Approach 2:
The counter DAI and total DAI fields provide feedback information from the base station's perspective about the scheduling state. This feedback mechanism allows the UE to verify and synchronize its understanding of the HARQ-ACK codebook structure with the base station, even in multi-carrier scenarios with multiple DCI formats, thereby maintaining codebook synchronization.
Data Source
AI summary
Embodiments of the present disclosure relate to methods and apparatuses for HARQ-ACK codebook determination. According to some embodiments of the disclosure, a method for wireless communications performed by a UE may include: receiving a plurality of DCI formats for scheduling PDSCH transmissions on a plurality of serving cells, wherein each of the plurality of DCI formats include a first indication information and a second indication information related to HARQ-ACK information for a PDSCH transmission scheduled by a corresponding DCI format; receiving the PDSCH transmissions based on the plurality of DCI formats; generating a HARQ-ACK codebook based on the first indication information and the second indication information in the plurality of DCI formats; and transmitting the HARQ-ACK codebook.