PDSCH Grouping for HARQ-ACK Reporting in 5G NR-U
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Solution Overview
Problem
In wireless communication systems, particularly in 5G NR-U, there is inefficiency in HARQ feedback transmission due to the uncertainty of LBT outcomes, leading to potential missed transmissions and unnecessary retransmissions, which result in inefficient band utilization and increased channel contention.
Innovation Solution
Implementing PDSCH grouping and a single-shot trigger mechanism, where the wireless device receives DCI to determine PDSCH groups and transmit HARQ-ACK reports based on configured group indices and indicators, allowing for coordinated feedback across multiple PDSCHs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HARQ feedback transmission is performed individually for each PDSCH, then the feedback timing can be precisely controlled, but the likelihood of missed transmissions increases due to LBT uncertainty
Solution Approach 1:
The patent combines multiple individual PDSCH feedback transmissions into a single group-level feedback transmission. By grouping multiple PDSCHs that share the same LBT outcome and transmitting their HARQ-ACK feedback together in one PUCCH, the system reduces the number of separate feedback transmissions required, thereby reducing the overall impact of LBT uncertainty and improving reliability.
Solution Approach 2:
The patent segments the feedback transmission process into two stages: first, individual PDSCHs are identified and grouped based on their scheduling DCI and LBT outcomes; second, grouped feedback is transmitted together. This segmentation allows the system to maintain precise timing control for individual PDSCHs while achieving the reliability benefits of coordinated group transmission.
2Reliability
If HARQ feedback is retransmitted upon missed detection, then the reliability of feedback delivery is improved, but bandwidth efficiency decreases due to unnecessary retransmissions
Solution Approach 1:
The patent performs preliminary grouping of PDSCHs before feedback transmission, organizing them into groups based on their scheduling relationships and LBT outcomes. This preliminary action ensures that feedback for multiple PDSCHs is coordinated and transmitted together, reducing the probability of missed detections and the need for subsequent retransmissions.
Solution Approach 2:
The patent implements a feedback mechanism where the gNB receives grouped HARQ-ACK feedback for multiple PDSCHs and uses this information to determine whether retransmissions are actually necessary. By evaluating the grouped feedback collectively, the gNB can avoid unnecessary individual retransmissions while maintaining reliable delivery of essential feedback.
3Loss of time
If individual PDSCH feedback transmissions are performed, then the feedback timing is precise, but channel contention increases due to multiple transmission opportunities
Solution Approach 1:
The patent merges multiple individual feedback transmission opportunities into a single coordinated transmission event for each group. By combining feedback for multiple PDSCHs into one PUCCH transmission, the system reduces the total number of uplink transmissions required, thereby reducing channel contention and the associated harmful effects while maintaining precise timing control through the grouping mechanism.
4Productivity
If PDSCH grouping is implemented, then bandwidth efficiency is improved by reducing missed transmissions, but the device complexity increases due to group management
Solution Approach 1:
The patent segments the PDSCH feedback process into manageable groups based on scheduling DCI relationships and LBT outcomes. This segmentation approach allows the system to implement grouping without requiring complex global coordination, as each group can be independently managed based on its specific characteristics, thereby reducing the overall device complexity while maintaining bandwidth efficiency benefits.
Data Source
AI summary
A wireless device receives downlink control information (DCI) from a network node, determines a physical downlink shared channel (PDSCH) group based on information in the received DCI, and transmits a hybrid automatic repeat request acknowledgement (HARQ-ACK) report to the network node based on the determined PDSCH group.