HARQ Feedback Scheduling for Multicast Retransmission Efficiency
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently managing HARQ retransmissions for multicast and broadcast transmissions, leading to resource wastage and reduced system performance due to extra decoding errors and unneeded NACK feedback.
Innovation Solution
A method involving a first node that transmits an initial HARQ feedback indicating ACK or NACK, receives a PDCCH for scheduling a PDSCH, and determines a target condition to send a subsequent NACK-only feedback based on previous decoding errors, optimizing resource utilization and reducing unnecessary retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HARQ feedback is transmitted for every retransmission in multicast/broadcast, then reliability is improved, but resource waste increases due to unneeded NACK feedback from UEs that already decoded successfully
Solution Approach 1:
The patent applies local quality by differentiating feedback behavior among different UEs based on their individual decoding status. UEs that successfully decode the initial transmission send ACK and stop receiving retransmissions, while UEs that fail to decode send NACK and continue receiving retransmissions. This localized differentiation eliminates unnecessary NACK feedback from successfully decoded UEs, reducing resource waste while maintaining reliability for those who need retransmissions.
Solution Approach 2:
The patent inverts the traditional HARQ feedback approach by using ACK-to-NACK indication. Instead of all UEs sending NACK by default and only successful decoders sending ACK, the system assumes successful decoding and requires only NACK from failed decoders. This inversion reduces feedback overhead significantly, as fewer UEs will need to send NACK compared to the traditional approach where most UEs might send ACK.
2Reliability
If retransmission is triggered by any NACK feedback, then decoding reliability is improved, but system performance deteriorates due to extra decoding errors from unnecessary retransmissions
Solution Approach 1:
The patent applies local quality by triggering retransmissions based on localized NACK feedback from specific UEs that failed to decode, rather than triggering retransmissions for all UEs whenever any NACK is received. This selective approach ensures retransmissions are only performed when actually needed by specific UEs, maintaining decoding reliability for those users while avoiding unnecessary retransmissions that would degrade overall system performance.
3Quantity of substance
If multiple UEs share the same PDCCH for multicast/broadcast, then resource utilization is improved, but difficulty in detecting and measuring feedback increases due to feedback collisions
Solution Approach 1:
The patent applies segmentation by dividing the feedback detection process into individual UE-level assessments. Each UE independently evaluates its own decoding status and sends feedback (ACK or NACK) based on its specific condition. The gNB processes feedback from each UE separately, determining retransmission needs on a per-UE basis. This segmentation eliminates feedback collisions by ensuring each UE's feedback is independently detected and processed, making feedback detection straightforward despite multiple UEs sharing the same PDCCH.
Data Source
AI summary
The present disclosure provides method and device in nodes used for wireless communication. A node transmits a first HARQ feedback, the first HARQ feedback being used to indicate either an ACK or a NACK; receives a first PDCCH, the first PDCCH being used to determine scheduling information for a first PDSCH; and determines whether a target condition is fulfilled, and, when the target condition is fulfilled, transmits a second HARQ feedback, the second HARQ feedback being only used to indicate a NACK; the first PDSCH is used for a retransmission of a first bit block; the first HARQ feedback is used for the first bit block, the first HARQ feedback being used to determine the target condition. The present disclosure improves the HARQ retransmission resource utilization ratio.