HARQ-ACK Codebook Segmentation for Mixed Priority Traffic
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Solution Overview
Problem
Current wireless communication systems face challenges in designing Hybrid Automatic Repeat Request (HARQ) Codebooks to support Intra-UE traffics with different priorities, particularly in 5G systems where High Priority and Low Priority transmissions overlap, leading to inefficiencies and potential dropping of Low Priority transmissions.
Innovation Solution
A method is proposed where HARQ-ACK associated with signalings in a time-frequency resource pool are structured with distinct priority fields, allowing for the differentiation and management of High Priority (URLLC) and Low Priority (eMBB) traffics, enabling effective multiplexing and avoiding transmission failures by reconsidering Downlink Assignment Index (DAI) mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If HARQ codebook is designed to support multiple priority traffics in the same time-frequency resource pool, then the system can multiplex High Priority and Low Priority transmissions, but the complexity of HARQ codebook design and DAI management increases
Solution Approach 1:
The HARQ codebook is segmented into separate parts for High Priority and Low Priority traffics. The DAI field is segmented into two separate fields: one for counting High Priority PDSCHs and another for Low Priority PDSCHs. This segmentation allows independent management of each priority level, reducing the complexity of managing mixed-priority codebooks while enabling efficient multiplexing.
Solution Approach 2:
Two separate DAI fields act as intermediaries between the scheduler and the HARQ-ACK feedback mechanism for different priority levels. The first DAI field counts High Priority PDSCHs while the second DAI field counts Low Priority PDSCHs, allowing the system to mediate between conflicting priority requirements without creating a single complex codebook structure.
2Reliability
If Low Priority transmission overlaps with High Priority transmission in time domain, then High Priority transmission is performed, but Low Priority transmission is dropped leading to loss of information
Solution Approach 1:
The system implements separate feedback mechanisms for High Priority and Low Priority transmissions through distinct DAI fields and HARQ-ACK codebook parts. When a Low Priority transmission overlaps with a High Priority transmission, the Low Priority transmission can still be acknowledged separately, providing feedback information that prevents complete information loss while ensuring High Priority reliability.
Solution Approach 2:
The scheduler performs preliminary counting of High Priority and Low Priority PDSCHs using separate DAI fields before transmitting data. This preliminary action allows the receiver to prepare appropriate HARQ-ACK feedback for each priority level, ensuring that even if Low Priority transmissions are dropped due to overlaps, the system has already established the framework for proper acknowledgment and potential retransmission.
3Device complexity
If a unified DAI field is used for counting both High Priority and Low Priority PDSCHs, then the signaling structure is simplified, but the ability to differentiate and manage different priority traffics is reduced
Solution Approach 1:
The unified DAI field is segmented into two separate fields: one dedicated to counting High Priority PDSCHs and another for Low Priority PDSCHs. This segmentation maintains relatively simple signaling structures for each priority level independently while providing the adaptability needed to differentiate and manage multiple priority traffics effectively.
Solution Approach 2:
Each DAI field is optimized for its specific priority level with local quality characteristics. The first DAI field is specifically designed for High Priority traffic management while the second DAI field is optimized for Low Priority traffic, allowing each field to have the appropriate properties for its intended purpose rather than forcing a single generic structure.
Data Source
AI summary
A first node monitors first-type signalings and second-type signalings in a first time-frequency resource pool, and receives a first signaling; and transmits a first information block. A second field comprised in each first-type signaling indicates a first priority, while a second field comprised in each second-type signaling indicates a second priority; when the first signaling is one of the first-type signalings, a value of a first field comprised in the first signaling is related to both a number of the first-type signalings and a number of the second-type signalings transmitted in the first time-frequency resource pool; when the first signaling is one of the second-type signalings, a value of a first field comprised in the first signaling is related to the number of the second-type signalings transmitted in the first time-frequency resource pool, rather than the number of the first-type signalings transmitted in the first time-frequency resource pool.