Sidelink HARQ Feedback Using Shared Channel Occupancy Time
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Solution Overview
Problem
In wireless communications systems operating in unlicensed spectrum, especially in Frame Based Equipment mode, network nodes face inefficiencies and delays due to the need for individual Clear Channel Assessments (CCA) before transmitting HARQ feedback on Physical Sidelink Feedback Channels (PSFCH), which can impact transmission reliability and resource utilization.
Innovation Solution
The proposed solution involves sharing channel occupancy time (COT) between UEs for PSFCH transmissions, where a transmitting UE shares its acquired COT with a receiving UE for HARQ feedback without initiating a new COT, indicated by sidelink control information (SCI), and optionally using cyclic prefix extensions to reduce gaps, thereby avoiding additional LBT procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a receiving UE performs individual CCA before transmitting HARQ feedback on PSFCH, then transmission reliability is improved by ensuring channel availability, but transmission delay increases and resource utilization deteriorates due to repeated LBT procedures
Solution Approach 1:
The patent merges the COT of the transmitting UE with the receiving UE for PSFCH transmission. The transmitting UE's COT is extended to include the PSFCH resources, allowing the receiving UE to transmit HARQ feedback without initiating a separate COT. This combining of COTs eliminates the need for repeated LBT procedures while maintaining channel availability assurance, thereby reducing transmission delay without compromising reliability.
2Reliability
If a receiving UE initiates a new COT for PSFCH transmission, then channel availability is ensured through independent CCA, but resource utilization deteriorates due to multiple LBT procedures occupying time resources
Solution Approach 1:
The patent makes the transmitting UE's COT universal by allowing it to serve both the PSSCH transmission and the PSFCH transmission. The COT indication in the SCI message specifies that the COT covers both the data channel and the feedback channel, enabling the receiving UE to use the same channel occupancy for both purposes. This multi-functionality of the COT ensures channel availability while improving resource utilization by eliminating redundant LBT procedures.
3Productivity
If COT sharing is implemented for PSFCH transmissions, then resource utilization improves by avoiding repeated LBT, but device complexity increases due to COT coordination mechanisms
Solution Approach 1:
The patent applies preliminary action by including the COT indication in the SCI message before the PSFCH transmission occurs. The transmitting UE specifies the COT duration and validity in advance, allowing the receiving UE to determine whether it can share the COT for PSFCH transmission without needing complex real-time coordination. This preliminary specification of COT parameters simplifies the device complexity while maintaining improved resource utilization.
Data Source
AI summary
Various aspects of the present disclosure relate to receiving sidelink control information (SCI) allocating resources for a physical sidelink shared channel (PSSCH) transmission, the SCI including a field indicating a channel occupancy time (COT) duration of a first COT, and transmitting hybrid automatic repeat request (HARQ) feedback in a physical sidelink feedback channel (PSFCH) transmission within the COT duration without initiating another COT based on the SCI. A receiving UE may determine the COT duration indicated by the SCI as shared for the transmission of the HARQ feedback on the PSFCH.