NR V2X HARQ Feedback Prioritization for Urgent NACK Transmission
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Solution Overview
Problem
In sidelink communication, the RX UE may drop physical sidelink feedback channel (PSFCH) transmission based on UL/SL prioritization, leading to transmission failures due to the TX UE determining successful decoding without receiving PSFCH, especially in NACK-only based hybrid automatic repeat request (HARQ) feedback operations.
Innovation Solution
A method and device for obtaining resource blocks for PSFCH transmission, receiving SCI for PSSCH scheduling, generating NACK information on MAC PDU failure, allocating RBs, determining a PSFCH resource index, and transmitting NACK based on a priority threshold, ensuring reliable communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the RX UE drops PSFCH transmission based on UL/SL prioritization procedure, then resource efficiency is improved, but transmission reliability deteriorates
Solution Approach 1:
The patent changes the priority parameter of NACK information from its original value to the highest priority when the remaining PDB is less than or equal to a threshold. This parameter change ensures that critical NACK feedback cannot be dropped by the prioritization procedure, resolving the contradiction between resource efficiency and transmission reliability for time-sensitive data.
Solution Approach 2:
The patent performs preliminary determination of the highest priority for NACK information based on the remaining PDB threshold before the prioritization procedure occurs. This preliminary action prevents the NACK from being dropped, ensuring reliable retransmission triggering for urgent data while still allowing normal prioritization for other feedback types.
2Speed
If the TX UE determines successful decoding without receiving PSFCH, then feedback processing speed is improved, but transmission reliability deteriorates
Solution Approach 1:
The patent applies preliminary anti-action by pre-determining that NACK information has the highest priority when remaining PDB is below the threshold. This prevents the problematic scenario where the TX UE would incorrectly determine successful decoding due to missing PSFCH, while still allowing fast feedback processing for non-critical data.
Solution Approach 2:
The patent enhances the feedback mechanism by ensuring that NACK feedback for time-sensitive data cannot be dropped during prioritization. This reliable feedback loop allows the TX UE to correctly identify decoding failures and perform necessary retransmissions, improving overall transmission reliability without significantly impacting processing speed.
Data Source
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AI summary
Provided are a method by which a first device performs wireless communication, and a device supporting same. The method may comprise the steps of: acquiring information regarding a set of resource blocks (RB) for physical sidelink feedback channel (PSFCH) transmission; receiving, from a second device, a physical sidelink shared channel (PSSCH) and first SCI for scheduling of second sidelink control information (SCI) through a physical sidelink control channel (PSCCH); receiving the second SCI including the source ID of the second device and a medium access control (MAC) protocol data unit (PDU) from the second device through the PSSCH, the first SCI or the second SCI including information regarding the remaining PDB of the MAC PDU; generating negative acknowledgement (NACK) information on the basis of a decoding failure related to the MAC PDU; allocating at least one RB among the set of RBs to the PSSCH; determining the index of a PSFCH resource for PSFCH transmission among the at least one RB on the basis of the source ID of the second device; determining that the priority of the NACK information is the highest priority on the basis of the remaining PDB being lower than or equal to a threshold; and transmitting the NACK information to the second device on the basis of the PSFCH resource.