Sidelink Feedback Resource Allocation in Unlicensed 5G V2X
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Solution Overview
Problem
The existing standards for 5G NR V2X do not effectively support HARQ-ACK retransmission in sidelink-unlicensed (SL-U) scenarios, particularly in Mode 1 resource allocation, where simultaneous retransmission of sidelink HARQ-ACK from a transmitting device to a network device and feedback from receiving devices is complex and inefficient.
Innovation Solution
A method and apparatus are provided to determine whether sidelink feedback information needs to be carried by a physical uplink control channel (PUCCH) and whether associated sidelink control and shared channels have been transmitted, preventing unnecessary PUCCH transmission and optimizing resource usage by determining PSFCH resources based on the number of sidelink feedback information bits, thereby reducing unlicensed frequency band occupation and avoiding collisions during HARQ-ACK retransmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PUCCH is transmitted to carry sidelink feedback information, then feedback reliability is improved, but unlicensed frequency band occupation increases and causes interference
Solution Approach 1:
The patent applies partial action by selectively transmitting PUCCH only when necessary. The transmitting device determines whether to transmit PUCCH based on whether sidelink feedback information was successfully received from the receiving device. If feedback is received, PUCCH transmission is skipped; if feedback is not received, PUCCH is transmitted to carry HARQ-ACK retransmission. This conditional transmission reduces unnecessary unlicensed band occupation while maintaining feedback reliability.
2Reliability
If HARQ-ACK retransmission is supported in SL-U Mode 1, then communication reliability is improved, but system complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where the receiving device sends sidelink feedback information (HARQ-ACK) to the transmitting device. The transmitting device uses this feedback to determine whether retransmission is needed. This feedback loop enables reliable HARQ-ACK retransmission in SL-U Mode 1 by allowing the system to adapt based on actual reception status, improving communication reliability without requiring complex predetermined retransmission schemes.
Solution Approach 2:
The system enables self-service through autonomous decision-making at the transmitting device. The device independently determines whether PUCCH transmission is needed by checking if sidelink feedback was received, and autonomously performs HARQ-ACK retransmission if necessary. This self-service approach reduces the need for complex network coordination and simplifies the overall system complexity while maintaining reliability.
3Ease of operation
If PUCCH is transmitted without checking feedback reception status, then transmission timing is simplified, but resource efficiency decreases
Solution Approach 1:
The patent applies preliminary action by having the transmitting device check the feedback reception status before deciding on PUCCH transmission. This pre-check allows the device to make an informed decision about whether transmission is necessary, avoiding unnecessary energy consumption and resource usage. The feedback status check is performed in advance of the PUCCH transmission decision, enabling efficient resource management while maintaining operational simplicity.
Data Source
AI summary
A method and an apparatus for transmitting and receiving sidelink feedback information. For HARQ-ACK retransmission from a first device to a network device, if the first device has transmitted a PSCCH and/or PSSCH associated with HARQ-ACK to a second device, but has not received sidelink feedback information needing to be carried by the PUCCH, the first device does not transmit the PUCCH to the network device, thereby unnecessary occupation of an unlicensed frequency band can be reduced or avoided, and the network device can be notified to schedule HARQ-ACK retransmission. For HARQ-ACK retransmission from the second device to the first device, a size of a HARQ-ACK codebook is additionally used to determine a PSFCH resource, so as to avoid a PSFCH resource collision during HARQ-ACK retransmission of multicast.