HARQ-ACK Codebook Reporting Under PUCCH Resource Collisions
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Solution Overview
Problem
In wireless communication systems, particularly in TDD bands, the cancellation of HARQ-ACK transmissions due to PUCCH resource collisions with invalid symbols or slots is costly, leading to inefficient retransmissions of dropped HARQ-ACK/NACK associated with many SPS PDSCHs.
Innovation Solution
The UE generates a HARQ-ACK codebook for SPS by deferring or delaying PUCCH transmissions to a next valid resource, using Type-3 or Type-1 HARQ-ACK codebooks, based on information and RRC messages from the base station.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If PUCCH transmissions are cancelled due to resource collisions with invalid symbols or slots, then resource conflicts are avoided, but HARQ-ACK feedback reliability deteriorates and retransmission costs increase
Solution Approach 1:
The system performs preliminary identification of valid PUCCH resources before transmission. The base station configures multiple PUCCH resources and the UE determines in advance which resources are valid (not in invalid symbols/slotes), selecting from these pre-identified valid resources to avoid collisions while ensuring reliable feedback transmission.
Solution Approach 2:
The base station acts as an intermediary by configuring and indicating valid PUCCH resources to the UE. Through RRC configuration and DCI indication, the base station mediates between the conflict of having PUCCH resources and avoiding invalid symbols/slotes, providing the UE with a set of pre-approved valid resources that eliminate the collision problem while maintaining feedback reliability.
2Loss of information
If HARQ-ACK feedback is reported for all DL HARQ processes, then feedback completeness is improved, but feedback reporting overhead increases
Solution Approach 1:
The system extracts and reports only the necessary HARQ-ACK feedback information. Instead of reporting feedback for all DL HARQ processes, the UE identifies and reports only for those processes that have actual data requiring acknowledgment, removing unnecessary feedback elements and reducing overhead while maintaining completeness for relevant data.
Solution Approach 2:
The system applies partial action by reporting HARQ-ACK feedback selectively rather than universally. The UE determines which specific HARQ processes require feedback based on actual downlink data reception, performing feedback action only where needed rather than excessive full coverage, thus reducing overhead while maintaining necessary completeness.
Data Source
AI summary
Aspects are provided which allow a UE to defer HARQ-ACK reporting in PUCCH transmissions according to a configured HARQ-ACK codebook. In one aspect, the UE receives, from a base station, information triggering feedback for DL HARQ processes of the UE, the UE receives a RRC message configuring the feedback to be for less than all of the DL HARQ processes, and the UE reports the feedback based on the information and the RRC message. In another aspect, the UE reports feedback including a plurality of HARQ-ACK bits in a PUCCH, where each of the HARQ-ACK bits is associated with DL data, and at least one of the DL data is associated with a cancelled PUCCH transmission. The UE may also append to the feedback a HARQ-ACK bit associated with other DL data, where the other data is associated with another cancelled PUCCH transmission.