Sidelink HARQ Process Selection for Adaptive NR V2X Retransmission
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Solution Overview
Problem
The management of sidelink Hybrid Automatic Repeat Request (HARQ) processes in New Radio (NR) V2X communication is unclear, particularly for different cast types and resource allocation modes, as LTE V2X HARQ operation is limited to blind retransmissions without feedback.
Innovation Solution
The proposed solutions outline methods for efficient sidelink HARQ protocol operation in NR V2X, including autonomous HARQ process selection by transmitting UEs, shared HARQ processes across different cast types and resource allocation modes, and switching transmission cast types for retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If blind retransmission is used without HARQ feedback, then device complexity is reduced, but communication reliability deteriorates
Solution Approach 1:
The patent implements HARQ feedback mechanisms where receiving UEs send ACK/NACK signals to transmitting UEs based on whether data was successfully decoded. This feedback enables adaptive retransmission decisions, improving reliability while maintaining manageable complexity through standardized feedback protocols.
Solution Approach 2:
The patent introduces dynamic HARQ process management where the transmitting UE can autonomously select HARQ process IDs and switch between different HARQ processes for initial transmissions and retransmissions. This dynamic approach allows flexible adaptation to channel conditions and traffic patterns without requiring complex centralized control.
2Adaptability or versatility
If autonomous HARQ process selection is implemented, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent enables transmitting UEs to autonomously manage their own HARQ processes by selecting HARQ process IDs and making retransmission decisions without network intervention. This self-service approach improves adaptability to local channel conditions while keeping implementation complexity manageable through standardized selection algorithms.
Solution Approach 2:
The patent divides HARQ management into separate functional components: HARQ process selection, data transmission, feedback reception, and retransmission decision-making. This segmentation allows each component to be implemented independently with standardized interfaces, reducing overall system complexity while maintaining high adaptability.
3Reliability
If HARQ feedback signaling is enabled, then communication reliability is improved, but loss of time increases due to feedback transmission
Solution Approach 1:
The patent implements mechanisms where HARQ feedback resources are pre-configured and allocated in advance, and where feedback is transmitted as soon as the receiving UE completes decoding. This preliminary preparation and immediate feedback transmission minimize the time loss associated with HARQ signaling while maintaining reliability improvements.
Solution Approach 2:
The patent employs periodic HARQ feedback mechanisms where feedback is transmitted at regular intervals corresponding to the transmission period. This periodic structure allows for predictable timing and efficient resource allocation, reducing overall time loss compared to asynchronous feedback approaches.
Data Source
AI summary
Apparatuses, methods, and systems are disclosed for sidelink HARQ operation. One apparatus includes a memory coupled to a processor, where the processor is configured to cause the second apparatus to receive a SL grant for a SL transmission using SL resources, the SL grant indicating a first HARQ process identified by a first HARQ process identifier, and to select a second SL HARQ process identified by a second SL HARQ process identifier for the SL transmission using the SL resources. The processor is configured to cause the second apparatus to transmit SCI containing the second SL HARQ process identifier and to perform the SL transmission using the SL resources.