HARQ-ACK Codebook Alignment When Downlink Feedback Is Disabled
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Solution Overview
Problem
In non-terrestrial networks with significant propagation delays, disabling Hybrid Automatic Repeat reQuest (HARQ) feedback can lead to misalignment in HARQ-ACK codebook sizes and unnecessary data bits, causing inefficiencies and misunderstandings between User Equipment (UE) and the Base Station (gNB).
Innovation Solution
The UE multiplexes HARQ-ACK information bits without including bits for downlink data transmissions with disabled HARQ feedback, and adjusts HARQ-ACK codebook sizes using counter and total Downlink Assignment Indicators (c-DAI and t-DAI) only for enabled HARQ processes, optimizing DCI formats to reduce redundant fields and align codebook sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If HARQ feedback is disabled for downlink data transmissions, then propagation delay issues in non-terrestrial networks are mitigated, but HARQ-ACK codebook size alignment and communication efficiency deteriorate
Solution Approach 1:
The patent applies local quality by differentiating HARQ feedback handling between enabled and disabled processes. The UE identifies which HARQ processes have feedback disabled and selectively excludes only those from HARQ-ACK codebook reporting, while maintaining normal reporting for enabled processes. This localized differentiation resolves the contradiction by preserving communication efficiency for enabled processes while accepting the time loss characteristic for disabled processes.
Solution Approach 2:
The patent segments the HARQ-ACK codebook into portions corresponding to enabled and disabled HARQ feedback processes. By segmenting the codebook construction and reporting mechanism, the system can independently handle different feedback scenarios, allowing disabled processes to be excluded from codebook size calculations while maintained processes continue to provide efficient feedback, thus resolving the productivity deterioration.
2Reliability
If HARQ-ACK information bits for disabled HARQ processes are included in the codebook, then codebook completeness is maintained, but codebook overhead and resource waste increase
Solution Approach 1:
The patent extracts and removes HARQ-ACK information bits corresponding to disabled HARQ feedback processes from the codebook. The UE identifies which processes have feedback disabled and excludes their associated bits from codebook construction. This extraction principle directly reduces codebook overhead and eliminates resource waste while maintaining reliability for enabled processes, as the codebook remains complete and accurate for all processes that actually require feedback.
3Adaptability or versatility
If DCI formats include all HARQ-related fields, then scheduling flexibility is maintained, but message size and processing complexity increase
Solution Approach 1:
The patent applies dynamics by making DCI format content adaptive based on HARQ feedback configuration. The DCI format dynamically includes or excludes HARQ-related fields depending on whether feedback is enabled for the associated process. This dynamic adaptation maintains scheduling flexibility when needed while reducing message size and processing complexity when feedback is disabled, resolving the contradiction between adaptability and device complexity.
Data Source
AI summary
A system and method for managing downlink data transmissions with HARQ feedback disabled. In some embodiments, the method includes: receiving, by a User Equipment (UE), a downlink data transmission with Hybrid Automatic Repeat reQuest (HARQ) feedback disabled; and multiplexing, by the UE, a plurality of HARQ-acknowledgment (HARQ-ACK) information bits to form a HARQ-ACK codebook, wherein the multiplexing of the HARQ-ACK information bits does not include multiplexing a HARQ-ACK information bit for the downlink data transmission in the HARQ-ACK codebook.