HARQ Feedback Mechanism for NR Uu Groupcast Reliability
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Solution Overview
Problem
In LTE MBMS, reliability is handled by the service layer or application layer, but this approach is insufficient for NR Uu groupcast use cases like V2X and IIoT, which require higher reliability and lower latency.
Innovation Solution
Introducing a HARQ feedback mechanism at the NR Uu interface to support transmission reliability, including methods for assigning and releasing groupcast RNTI, enabling and disabling HARQ feedback, and handling collisions between HARQ feedback and other transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HARQ feedback mechanism is introduced to NR Uu groupcast, then transmission reliability is improved, but system complexity increases
Solution Approach 1:
The patent segments the HARQ feedback mechanism by introducing separate RNTI types (G-RNTI for groupcast, B-RNTI for broadcast) and separate feedback channels (PUCCH for groupcast, PUCCH/PUSCH for broadcast). This segmentation allows independent optimization of reliability for different transmission types while managing system complexity through modular design.
Solution Approach 2:
The patent implements feedback mechanisms where UEs send HARQ feedback (ACK/NACK) to the gNB to indicate successful reception or failure of groupcast transmissions. This feedback loop enables the gNB to adjust transmission parameters and improve reliability through adaptive retransmission strategies.
2Reliability
If HARQ feedback is enabled for all groupcast transmissions, then reliability is improved, but latency increases
Solution Approach 1:
The patent dynamically configures HARQ feedback parameters including feedback timing indicators, feedback resource allocation, and feedback enabling/disabling based on transmission conditions. This dynamic adjustment allows the system to optimize between reliability and latency by enabling feedback only when necessary and adjusting feedback timing to minimize delays.
Solution Approach 2:
The patent implements periodic HARQ feedback mechanisms where feedback is transmitted in periodic intervals rather than continuously. The feedback timing indicator specifies periodic feedback occasions, allowing reliability to be maintained through regular feedback while reducing latency by avoiding continuous feedback overhead.
3Measurement precision
If multiple PUCCH resources are allocated for HARQ feedback, then feedback accuracy is improved, but resource utilization efficiency decreases
Solution Approach 1:
The patent merges multiple PUCCH resources into a single PUCCH resource for HARQ feedback transmission, combining the feedback from multiple UEs in one resource allocation. This merging approach maintains feedback accuracy by collecting ACK/NACK information from all UEs while improving resource utilization efficiency by reducing the total number of resources required.
Solution Approach 2:
The patent designs the PUCCH resource to serve multiple functions: it can carry HARQ feedback for different groups of UEs, support both groupcast and broadcast feedback, and accommodate varying feedback configurations through universal resource allocation mechanisms. This multi-functionality improves resource utilization efficiency while maintaining feedback accuracy.
Data Source
AI summary
Disclosed herein are methods and apparatus for HARQ feedback in NR Uu groupcast or broadcast, including methods for assigning and releasing the groupcast RNTI for Uu groupcast or broadcast, methods for enabling and disabling the HARQ feedback for Uu groupcast or broadcast, and methods for HARQ feedback and corresponding resource allocation for Uu groupcast or broadcast, including ACK-NACK based Uu groupcast HARQ feedback, NACK only based Uu groupcast HARQ feedback, and Enhanced ACK-NACK based Uu groupcast HARQ feedback. Also disclosed herein are methods for collision handling between HARQ feedback for Uu broadcast/groupcast and other transmissions.