Multicast HARQ Feedback with Per-Service DAI Counters
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Solution Overview
Problem
The challenge in implementing hybrid automatic repeat request (HARQ) mechanisms for multicast and broadcast services (MBS) lies in structuring HARQ feedback and constructing uplink grants when multiple MBS services are provided, as existing mechanisms do not clearly define how a UE should format a type-2 HARQ codebook or how a base station should use a single uplink DAI to convey information for multiple MBS services.
Innovation Solution
A method for UEs and base stations to implement a dynamic HARQ feedback mechanism by using separate DAI counters for each MBS service, appending additional information to sub-codebooks, and employing a single uplink grant to manage HARQ feedback for multiple MBS services, ensuring accurate reporting of feedback even if some MBS services are missed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single uplink DAI is used to convey information for multiple MBS services, then the uplink grant structure is simplified, but it becomes difficult to accurately convey information for each individual MBS service
Solution Approach 1:
The patent segments the feedback reporting mechanism by introducing separate downlink DAI (DL-DAI) counters for each MBS service. This allows the base station to track and indicate the total number of downlink assignments for each specific MBS service independently, enabling accurate feedback reporting for multiple services while maintaining a unified uplink grant structure.
Solution Approach 2:
The patent makes the uplink DAI field universal by enabling it to convey information for multiple MBS services simultaneously. The single uplink DAI field in the uplink grant can indicate the total number of downlink assignments across all configured MBS services, allowing one field to serve multiple services without requiring separate uplink grants for each service.
2Measurement precision
If separate DAI counters are used for each MBS service, then accurate tracking of downlink assignments is achieved, but the complexity of HARQ codebook construction increases
Solution Approach 1:
The patent implements a feedback mechanism where the base station sends DL-DAI values in downlink assignments for each MBS service, and the UE uses these values to construct the HARQ codebook. The DL-DAI indicates the cumulative number of downlink assignments for each service, enabling the UE to accurately determine which services have been missed and construct the appropriate codebook without excessive complexity.
3Adaptability or versatility
If a type-2 HARQ codebook is used for dynamic feedback, then flexibility in reporting is improved, but the difficulty of formatting and structuring the codebook increases
Solution Approach 1:
The patent changes key parameters of the type-2 HARQ codebook structure to simplify formatting. By using separate DL-DAI counters for each MBS service and having the base station indicate the total number of downlink assignments, the UE can more easily determine the codebook size and structure. The parameters governing codebook construction are made more explicit through the DL-DAI mechanism, reducing the complexity of dynamic codebook formatting.
Data Source
AI summary
A user equipment (UE) can implement a method for reporting feedback for a multicast and/or broadcast service (MBS) when the UE is receiving multiple MBSs. The method may include receiving (402), during a time period when a base station generates a sequence of downlink assignments for the multiple MBSs, a plurality of downlink assignments included in the sequence of the downlink assignments, the plurality of downlink assignments scheduling a respective plurality of data transmissions of the MBS service; attempting to receive (404), from the base station, the plurality of data transmissions in accordance with the plurality of downlink assignments; and transmits (406), to the base station, feedback for the plurality of data transmissions, the feedback including an indication of a last successfully received downlink assignment of the plurality of downlink assignments.