Base Station DAI Configuration for HARQ-ACK Codebook Alignment
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Solution Overview
Problem
Current 5G NR systems face inefficiencies in retransmission control, particularly in non-terrestrial networks where long round trip times and feedback-disabled HARQ processes can lead to misalignment in HARQ-ACK codebook sizes between base stations and terminals, affecting data transmission reliability and efficiency.
Innovation Solution
The implementation of a method that uses Downlink Assignment Index (DAI) to configure and transmit information about the number of data assignments in the retransmission process, enabling terminals to correctly determine the HARQ-ACK codebook size even in cases of DCI reception failures, and optimizing feedback configurations for HARQ processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If feedback is disabled for HARQ processes in non-terrestrial networks, then device complexity is reduced, but reliability of retransmission control deteriorates due to misalignment in HARQ-ACK codebook sizes
Solution Approach 1:
The base station performs preliminary action by determining and configuring DAI information before data transmission. The DAI is configured based on the feedback configuration (enabled or disabled) and indicates the number of data assignments. This preliminary configuration allows the terminal to correctly determine HARQ-ACK codebook size even when feedback is disabled, preventing misalignment issues before they occur.
2Measurement precision
If DAI information is configured based on feedback configuration, then reliability of HARQ-ACK codebook size recognition is improved, but device complexity increases due to additional configuration parameters
Solution Approach 1:
The DAI configuration is made local to each HARQ process's feedback configuration. When feedback is enabled, DAI is configured to indicate the number of data assignments for that specific HARQ process. When feedback is disabled, DAI is configured differently (e.g., set to a fixed value or not configured). This localized configuration approach ensures accurate HARQ-ACK codebook size recognition for each case without requiring a complex unified configuration system.
Data Source
AI summary
This base station is provided with: a control circuit which determines information to be set in a signal for notifying a number of data allocations in a retransmission process, on the basis of a setting relating to feedback for the retransmission process; and a transmission circuit for transmitting the information in the signal.