C-DAI and T-DAI Segmentation for Multi-PDSCH HARQ Codebooks
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Solution Overview
Problem
In the 5G New Radio (NR) system, determining the size of a HARQ codebook is challenging when single DCI schedules multiple PDSCHs, leading to incorrect feedback due to missed detections, as existing DAI methods are inadequate for multiple PDSCH scenarios.
Innovation Solution
Configuring the Downlink Assignment Indicator (DAI) with C-DAI field indication information to indicate the cumulative number of PDSCHs scheduled by a PDCCH up to a current serving cell and monitoring occasion, combined with T-DAI for the total number, enabling accurate determination of missed detections and improving HARQ codebook accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If single DCI schedules multiple PDSCHs, then scheduling efficiency is improved, but HARQ codebook determination accuracy deteriorates
Solution Approach 1:
The patent segments the DAI into two independent fields: C-DAI (Counter DAI) that counts PDSCHs per PDCCH monitoring occasion, and T-DAI (Total DAI) that counts total PDSCHs across all monitoring occasions. This segmentation allows the UE to accurately determine the number of PDSCHs even when multiple PDSCHs are scheduled by a single DCI, resolving the contradiction between scheduling efficiency and HARQ codebook determination accuracy.
2Device complexity
If existing DAI method is used, then simplicity is maintained, but feedback accuracy deteriorates in multiple PDSCH scenarios
Solution Approach 1:
The patent divides the DAI into C-DAI and T-DAI fields with distinct functions. C-DAI tracks the cumulative number of PDSCHs per PDCCH monitoring occasion, while T-DAI tracks the total number of PDSCHs. This segmentation enables accurate feedback even in complex multiple PDSCH scenarios without significantly increasing implementation complexity.
Solution Approach 2:
The patent introduces a feedback mechanism where the UE uses both C-DAI and T-DAI to determine the number of PDSCHs and generate accurate HARQ codebooks. The feedback includes ACK/NACK information for each PDSCH, allowing the base station to correctly identify missed detections and adjust retransmission strategies.
3Ease of operation
If UE determines PDSCH number based on received DAI, then processing simplicity is maintained, but missed detection discovery capability deteriorates
Solution Approach 1:
The patent enables missed detection discovery by comparing C-DAI (cumulative PDSCH count per monitoring occasion) with T-DAI (total PDSCH count). When the UE receives DCI with multiple PDSCHs scheduled, it can determine the expected number of PDSCHs based on C-DAI and compare it with the actual number received. Any discrepancy indicates missed detections, allowing the UE to discover and report these errors in the HARQ feedback.
Data Source
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AI summary
A method and device for determining a downlink assignment indicator, a method and device for configuring a downlink assignment indicator, a storage medium, a terminal, and a base station. The determination method comprises: receiving DCI including C-DAI field indication information, wherein the C-DAI field indication information is used to indicate the cumulative total number of PDSCHs scheduled by a PDCCH up until the current serving cell and the current PDCCH monitoring occasion; and determining a HARQ codebook according to the DCI. The present invention enables UE to promptly acquire the number of missed PDSCH detections, thereby improving the accuracy of a HARQ codebook.