HARQ-ACK Codebook Timing for 5G NR-U Frame-Based Operation
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Solution Overview
Problem
The lack of detailed methods for determining semi-static HARQ-ACK codebooks for frame-based equipment (FBE) operation in 3GPP 5G NR-U, leading to misunderstandings between UE and BS on HARQ-ACK codebook size and inefficient HARQ-ACK feedback transmission.
Innovation Solution
Implementing multiple K1 sets for configuring HARQ feedback timing, including intra-FFP and cross-FFP HARQ-ACK feedback, with dynamic indication of a specific K1 set based on postponed HARQ-ACK feedback presence, and constructing a final HARQ-ACK codebook with separate sub-codebooks for postponed and non-postponed feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a UE operates in unlicensed spectrum with both frame-based equipment (FBE) and grant-based equipment (GBE), then spectrum utilization is improved, but HARQ-ACK feedback timing conflicts occur due to different frame structures
Solution Approach 1:
The patent segments the HARQ-ACK feedback mechanism into separate codebooks for FBE and GBE operations. The FBE HARQ-ACK codebook is determined independently based on FBE downlink assignments, while the GBE HARQ-ACK codebook is determined based on GBE downlink assignments. This segmentation allows each codebook to be constructed according to its respective frame structure requirements, eliminating timing conflicts while maintaining high spectrum utilization in unlicensed spectrum
Solution Approach 2:
The patent implements dynamic determination of FBE HARQ-ACK codebook size and content based on the actual FBE downlink assignment indicator (DAI) values received. The codebook is dynamically adjusted to match the varying timing relationships between FBE downlink transmissions and uplink feedback opportunities, allowing the system to adapt to different frame structures and scheduling conditions in real-time
2Use of energy by moving object
If FBE uses fixed frame structure with periodic listening intervals, then power consumption is reduced, but flexibility in HARQ-ACK timing alignment with GBE is lost
Solution Approach 1:
The patent applies preliminary action by determining the FBE HARQ-ACK codebook structure in advance based on the FBE DAI values received in each downlink assignment. The codebook is prepared with the appropriate number of bits and timing relationships before the actual uplink transmission occurs. This allows the FBE to maintain its fixed frame structure and periodic listening intervals for power efficiency, while still achieving proper HARQ-ACK timing alignment through pre-computed codebook configurations
3Measurement precision
If separate HARQ-ACK codebooks are maintained for FBE and GBE, then feedback accuracy is improved, but uplink resource requirements increase
Solution Approach 1:
The patent implements partial action by transmitting only the necessary portions of HARQ-ACK feedback in each uplink opportunity. The FBE HARQ-ACK codebook contains only the feedback bits corresponding to FBE downlink assignments, while the GBE HARQ-ACK codebook contains only GBE feedback bits. Each codebook is sized precisely to match the number of downlink assignments received, avoiding transmission of unnecessary feedback bits and optimizing uplink resource utilization
Data Source
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AI summary
The present application is related to a method and apparatus for semi-static hybrid automatic repeat request acknowledgement (HARQ-ACK) codebook determination for FBE operation under 3GPP 5G new radio (NR). A method for wireless communications performed by a UE includes: receiving downlink control information (DCI) for scheduling a data transmission in a current periodic channel occupancy; determining whether there is HARQ-ACK feedback corresponding to a data transmission postponed in an earlier periodic channel occupancy; and transmitting a HARQ-ACK codebook in the current periodic channel occupancy, wherein, in response to determining that there is the HARQ-ACK feedback corresponding to the data transmission postponed in the earlier periodic channel occupancy, the HARQ-ACK codebook comprises HARQ-ACK feedback corresponding to the data transmission in the current periodic channel occupancy and the postponed HARQ-ACK feedback corresponding to the data transmission in the earlier periodic channel occupancy.