HARQ Feedback Triggering for Low-Latency UE TX/RX

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Solution Overview

Problem

Existing wireless communication systems, particularly in 5G NR, face challenges in reducing latency and overhead associated with retransmissions and channel sounding after failed physical downlink shared channel (PDSCH) transmissions, necessitating improved mechanisms for feedback-based triggering of transmissions and receptions.

Innovation Solution

Implementing a feedback mechanism that utilizes negative-acknowledgment (NACK) to trigger sounding reference signal (SRS) transmissions, channel state information-reference signal (CSI-RS) transmissions, and sidelink retransmissions by determining combined feedback from multiple ACK/NACK bits, with triggers based on threshold percentages or specific bit conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional retransmission mechanisms are used in 5G NR, then communication reliability is maintained, but latency and control overhead increase

Engineering Contradiction:
Improvecommunication reliabilityVSAvoidlatency
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by pre-configuring resources for retransmission and channel sounding before they are actually needed. When a NACK is received, the system can immediately activate pre-prepared resources rather than going through lengthy scheduling procedures, thus reducing latency while maintaining reliability

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback-based triggering where NACK feedback from the UE directly triggers retransmission and channel sounding operations. This closed-loop feedback mechanism ensures reliable communication by responding to actual transmission failures while minimizing unnecessary retransmissions that would increase latency

Inventive Principle:
Principle #23Feedback

2Reliability

If traditional retransmission mechanisms are used in 5G NR, then communication reliability is maintained, but downlink control information scheduling overhead increases

Engineering Contradiction:
Improvecommunication reliabilityVSAvoidcontrol overhead
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the triggering decision from the complex downlink control information scheduling process. By using simple NACK feedback as a direct trigger for retransmission and channel sounding, the system removes the need for extensive DCI scheduling overhead while maintaining reliable communication through feedback-based activation

Inventive Principle:
Principle #2Taking out (Extraction)

3Reliability

If combined feedback from multiple ACK/NACK bits is processed, then communication reliability is enhanced, but feedback processing complexity increases

Engineering Contradiction:
Improvecommunication reliabilityVSAvoidfeedback processing complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies partial action by focusing processing only on the necessary feedback bits. Instead of processing all possible feedback scenarios equally, the system selectively processes combined ACK/NACK bits based on specific triggering conditions (such as threshold percentages), reducing complexity while enhancing reliability through targeted feedback analysis

Inventive Principle:
Principle #16Partial or excessive action

Data Source

PatentEP4208971B1Feedback triggered TX/RX for a UE based on multiple ACK/nack
Publication Date: 2025.11.19 QUALCOMM INC
  • EP4208971B1 patent drawingFigure 1
  • EP4208971B1 patent drawingFigure 2A~2D
  • EP4208971B1 patent drawingFigure 3

AI summary

This disclosure provides systems, devices, apparatus, and methods, including computer programs encoded on storage media, for ACK/NACK-triggered communications with a UE based on multiple ACK/NACK bits in HARQ feedback from a UE. The UE may receive a configuration for a resource, monitor for one or more PDSCH transmissions, and transmit an uplink transmission including HARQ feedback carrying multiple NACK or ACK bits for the one or more PDSCH transmissions. The UE may transmit or receive communication in the resource based on a trigger in the HARQ feedback for transmission or reception of the communication in the resource.