Cross-COT HARQ Feedback for Sidelink Unlicensed Spectrum
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Solution Overview
Problem
HARQ feedback transmissions in NR V2X sidelink communications using unlicensed spectrum face uncertainty due to shared channel availability and regulatory requirements, leading to potential time delays and unavailability of resources for HARQ feedback in the same channel occupancy time (COT), especially in the last slots of a COT.
Innovation Solution
Implement cross channel occupancy time (COT) hybrid automatic repeat request (HARQ) feedback techniques that allow HARQ feedback to be transmitted in adjacent or subsequent COTs, utilizing Type 2 or Type 1 channel access methods to ensure availability of resources for HARQ feedback, even when the initial COT expires or is not available.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If HARQ feedback is transmitted within the same COT, then spectral efficiency is improved, but resource availability becomes uncertain especially in the last slots of COT
Solution Approach 1:
The patent segments the HARQ feedback transmission into two distinct scenarios: same-COT feedback and cross-COT feedback. This segmentation allows the system to adaptively select the appropriate feedback mechanism based on resource availability, ensuring that feedback can be transmitted reliably whether within the same COT or across COT boundaries.
Solution Approach 2:
The patent introduces an intermediary mechanism through pre-configured feedback resources and alternative feedback occasions that act as mediators when primary same-COT feedback resources are unavailable. This intermediary approach ensures continuous feedback capability by providing fallback options in adjacent or subsequent COTs.
2Reliability
If HARQ feedback processing time is extended to ensure transmission in available COTs, then reliability is improved, but system latency increases
Solution Approach 1:
The patent applies preliminary action by pre-configuring multiple feedback resources and alternative feedback occasions before HARQ feedback is actually needed. This advance preparation ensures that when feedback transmission is required, suitable resources are already available, eliminating the need for extended processing time to search for or establish feedback channels.
Solution Approach 2:
The patent introduces dynamic selection of feedback occasions based on actual channel conditions and COT availability. The receiving UE can dynamically choose between same-COT feedback (when available) and cross-COT feedback (when same-COT resources are unavailable), optimizing the balance between reliability and latency based on real-time conditions.
3Reliability
If Type 1 or Type 2 channel access methods are used for cross-COT feedback, then feedback availability is ensured, but device complexity increases
Solution Approach 1:
The patent changes the parameter of channel access type selection based on feedback occasion location. When feedback is transmitted in the same COT, simpler procedures are used. When cross-COT feedback is required, the system transitions to Type 1 or Type 2 channel access procedures. This parameter change approach ensures feedback availability while minimizing complexity by only applying more complex procedures when necessary.
Data Source
AI summary
Techniques for cross channel occupancy time (COT) hybrid automatic repeat request (HARQ) feedback transmission for sidelink communication in unlicensed spectrum may be performed. In an example, a receiving user equipment (UE) may receive, from a transmitting UE, a first transmission in a first channel occupancy time (COT). The receiving UE may also determine a first feedback occasion is after a last slot of the first COT. The receiving UE may also determine one or more feedback configurations. The receiving UE may also transmit, to the transmitting UE, a feedback message indicating decoding of the first transmission in the first feedback occasion or a second feedback occasion based on the one or more feedback configurations.