NR V2X Sidelink HARQ Buffer Flushing With Dynamic Grant Timer

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Solution Overview

Problem

In NR sidelink communication, the UE may face power-saving issues related to DG-based HARQ processes due to the lack of limitations on when a CG resource with the same HARQ process ID appears in another CG period.

Innovation Solution

A method and apparatus for performing wireless communication involving a first device that receives a dynamic grant, transmits a transport block based on a sidelink resource, receives sidelink HARQ negative acknowledgment (NACK) information, and transmits the NACK to a base station, starting a timer upon NACK transmission, and flushing the buffer upon timer expiration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If DG-based HARQ process is used in NR sidelink communication without limitations on CG resource appearance, then flexibility in resource allocation is improved, but power consumption increases due to lack of buffer flushing mechanism

Engineering Contradiction:

Improveflexibility in resource allocationVSAvoidpower consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The patent changes the state of the HARQ buffer by introducing a timer mechanism that transitions the buffer from an active state (holding transport blocks) to a flushed state (empty) when the timer expires. This parameter change (buffer state) directly addresses the power consumption issue while maintaining allocation flexibility

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system serves itself by automatically flushing the HARQ buffer when the timer expires without requiring external intervention. The timer mechanism autonomously manages the buffer state based on the absence of retransmission grants, eliminating the need for continuous power consumption to maintain buffer contents

Inventive Principle:

Principle #25Self-service

2Reliability

If DG-based HARQ process allows indefinite buffer retention, then retransmission reliability is improved, but resource utilization deteriorates due to unnecessary power consumption

Engineering Contradiction:

Improveretransmission reliabilityVSAvoidunnecessary power consumption

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent implements a periodic timer mechanism that automatically checks and flushes the HARQ buffer at predetermined intervals. This periodic action ensures that the buffer is retained only as long as necessary for retransmissions, and automatically cleared when no further retransmissions are scheduled, eliminating unnecessary power consumption while maintaining reliability

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS12610359B2Method and apparatus for operating HARQ process in NR V2X

Publication Date: 2026.04.21 LG ELECTRONICS INC

AI summary

Proposed is a method by which a first device performs wireless communication. The method may comprise the steps of: receiving, from a base station, a first dynamic grant through a physical downlink control channel (PDCCH); transmitting, to a second device, a transport block on the basis of a sidelink resource allocated by the first dynamic grant; receiving, from the second device, sidelink hybrid automatic repeat request negative acknowledgment (SL HARQ NACK) information related to the transport block; and transmitting, to the base station, the SL HARQ NACK information through a physical uplink control channel (PUCCH). For example, on the basis of transmitting the SL HARQ NACK information to the base station, a timer related to the first dynamic grant may be initiated. For example, on the basis of the timer expiring, a buffer related to the transport block may be flushed.