Downlink Assignment Index Alignment for Multi-TRP HARQ Feedback
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Solution Overview
Problem
Existing wireless communication systems face challenges in achieving high reliability and low latency for enhanced URLLC (eURLLC) applications, particularly in scenarios involving multiple TRPs and carrier aggregation, where conventional DAI mechanisms are inadequate.
Innovation Solution
An enhanced DAI mechanism is introduced, combined with HARQ feedback, to align DAI values across multiple downlink control channels, enabling efficient HARQ codebook generation and improved reliability by ensuring identical DAI values for associated transport blocks, even in multi-TRP and multi-carrier scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple PDCCHs are transmitted from multiple TRPs to schedule transport blocks, then reliability is improved, but DAI value alignment becomes complex and HARQ codebook overhead increases
Solution Approach 1:
The patent applies parameter changes by modifying the DAI value assignment strategy. Instead of using sequential or TRP-specific DAI values, the invention assigns identical DAI values to multiple PDCCHs scheduling the same transport block. This parameter change simplifies the DAI alignment mechanism while maintaining reliability through multiple PDCCH transmissions from different TRPs.
Solution Approach 2:
The patent inverts the conventional approach by not using distinct DAI values for different TRPs. Instead, it uses the same DAI value across multiple TRPs for the same transport block, which simplifies the HARQ codebook generation at the UE side and reduces overhead while maintaining the reliability benefits of multi-TRP transmission.
2Loss of information
If DAI values are aligned across multiple downlink control channels, then HARQ codebook overhead is reduced, but the complexity of coordinating DAI assignment across multiple TRPs increases
Solution Approach 1:
The patent merges the DAI value assignment across multiple TRPs by using a common DAI value for scheduling the same transport block. This merging approach reduces HARQ codebook overhead at the UE side, as the UE can generate a compact codebook based on aligned DAI values, while the coordination complexity is managed at the network side through centralized or pre-configured DAI assignment rules.
3Productivity
If identical DAI values are assigned to multiple PDCCHs scheduling the same transport block, then HARQ feedback efficiency is improved, but the ability to distinguish between different scheduled blocks is reduced
Solution Approach 1:
The patent resolves the distinction problem by moving from DAI value differentiation to other dimensional differentiation. While DAI values are identical, the PDCCHs are distinguished by other parameters such as time resources, frequency resources, spatial parameters (beam directions), or TRP identifiers. This dimensional change allows the UE to correctly identify and process multiple PDCCHs with the same DAI value without confusion.
Data Source
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AI summary
The invention relates to a client device and a serving device for enhanced downlink assignment index indication. The client device (100) obtains a first DAI in a first downlink control channel (522) associated with transmission of a first transport block, wherein the first DAI indicates a first scheduling assignment for the first transport block. The client device (100) further obtains a second DAI in a second downlink control channel (524) associated with transmission of a second transport block, wherein the second DAI indicates a second scheduling assignment for the second transport block. The client device (100) finally determines that at least one value of the second DAI is an assigned value identical to a value of the first DAI. Thereby, downlink control channel reliability is increased and/or that the blocking rate of downlink control channel is reduced. Furthermore, the invention also relates to corresponding methods and a computer program.