Tri-State HARQ-ACK Codebook Determination for 5G NR
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Solution Overview
Problem
Current wireless communication systems, particularly in 5G NR, face inefficiencies in HARQ feedback mechanisms, as they cannot accurately distinguish between decoding failures of the PDCCH and PDSCH, leading to unnecessary retransmissions and suboptimal resource allocation.
Innovation Solution
The implementation of a tri-state HARQ feedback system, which includes ACK, NACK, and DTX states, allows user equipment (UE) to provide detailed feedback on the decoding success of both PDCCH and PDSCH, enabling the base station to identify specific decoding failures and optimize retransmission strategies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If bi-state HARQ feedback (ACK/NACK) is used, then the feedback mechanism is simple and resource overhead is low, but the system cannot accurately distinguish between PDCCH decoding failures and PDSCH decoding failures, leading to unnecessary retransmissions
Solution Approach 1:
The patent segments the HARQ feedback into distinct states: ACK for PDSCH decoding success, NACK for PDSCH decoding failure, and DTX for PDCCH decoding failure. This segmentation allows the system to precisely identify the type of decoding failure without increasing overall feedback complexity, as each state has a clear, predefined meaning that simplifies base station interpretation and retransmission decision-making.
2Reliability
If tri-state HARQ feedback (ACK/NACK/DTX) is implemented, then the accuracy of decoding failure identification is improved, but the feedback overhead and processing complexity increase
Solution Approach 1:
The patent implements a self-service mechanism where the UE autonomously determines whether to transmit ACK, NACK, or DTX based on its own decoding results of PDCCH and PDSCH. This self-determination eliminates the need for additional base station signaling to query feedback status, reducing feedback overhead while maintaining high retransmission efficiency through accurate failure identification.
3Productivity
If detailed feedback on both PDCCH and PDSCH decoding is provided, then resource allocation efficiency is improved, but the processing complexity at UE increases
Solution Approach 1:
The patent changes the feedback parameter from a simple binary ACK/NACK to a tri-state ACK/NACK/DTX system. This parameter change enables the UE to convey additional information about PDCCH decoding status without requiring complex processing algorithms. The base station uses this enriched parameter to efficiently allocate retransmission resources, improving overall system productivity while keeping UE processing manageable through straightforward state determination.
Data Source
AI summary
Aspects presented herein may enhance a HARQ feedback operation to improve data retransmissions by using tri-state HARQ feedback, and may enable a UE to construct a codebook for tri-state HARQ feedback. In one aspect, a UE determines whether tri-state HARQ feedback or bi-state HARQ feedback is configured based on a DL carrier. The UE generates HARQ feedback for at least one of a received PDCCH or a received PDSCH on the DL carrier based on the determination whether the DL carrier is configured with the tri-state HARQ feedback. The UE transmits the generated HARQ feedback.