UE Out-of-Order HARQ-ACK Processing for URLLC Latency
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Solution Overview
Problem
Current wireless communication systems, particularly in Rel-15, face challenges in optimizing latency for ultra-reliable low latency communication (URLLC) due to restrictions in scheduling and hybrid automatic repeat request (HARQ) acknowledgment (ACK) reporting, where overlapping PDSCHs cannot be processed efficiently, leading to increased end-to-end latency.
Innovation Solution
The system introduces a method to determine and apply a delay in processing time for HARQ-ACK corresponding to a second PDSCH based on overlapping time with a first PDSCH, allowing for earlier transmission of HARQ-ACK for high-priority URLLC traffic, thereby reducing latency by increasing the processing time of the second PDSCH by a calculated amount, ensuring timely processing of high-priority channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If in-order HARQ-ACK and in-order PDSCH operations are used in Rel-15, then scheduling simplicity is maintained, but end-to-end latency increases for URLLC traffic
Solution Approach 1:
The patent inverts the traditional in-order processing approach by implementing out-of-order HARQ-ACK reporting and out-of-order PDSCH processing. Specifically, when a high-priority PDSCH (e.g., URLLC) overlaps with a low-priority PDSCH (e.g., eMBB), the UE processes and reports HARQ-ACK for the high-priority PDSCH before completing processing of the low-priority PDSCH, thereby reducing end-to-end latency while maintaining scheduling simplicity through standard Rel-15 mechanisms
Solution Approach 2:
The patent changes the processing order parameter from fixed in-order to dynamic out-of-order based on traffic priority. The UE determines processing priority by comparing priority indicators (e.g., QoS parameters, RNTI values) of overlapping PDSCHs and adjusts the HARQ-ACK reporting sequence accordingly, allowing high-priority traffic to be processed ahead of low-priority traffic without requiring new scheduling protocols
2Ease of manufacture
If eMBB traffic is scheduled first and URLLC traffic arrives later, then resource allocation simplicity is maintained, but URLLC latency increases due to inability to schedule until eMBB ends
Solution Approach 1:
The patent introduces dynamic resource allocation where the processing order of PDSCHs is not fixed but adapts based on real-time priority assessment. When URLLC traffic arrives and overlaps with eMBB traffic, the system dynamically switches to process URLLC first by detecting the priority difference and adjusting the HARQ-ACK reporting timeline, enabling URLLC to be scheduled and acknowledged before eMBB completes without requiring complex re-scheduling
3Stability of the object's composition
If HARQ-ACK for URLLC PDSCH is transmitted after eMBB PDSCH HARQ-ACK, then in-order processing is maintained, but URLLC latency requirement is not met
Solution Approach 1:
The patent inverts the HARQ-ACK reporting order by prioritizing high-priority PDSCH acknowledgments over low-priority ones. When overlapping PDSCHs are detected, the UE identifies the high-priority PDSCH through priority indicator comparison and transmits its HARQ-ACK in an earlier uplink opportunity (e.g., earlier PUCCH or PUSCH slot) than the low-priority PDSCH HARQ-ACK, achieving out-of-order reporting that reduces URLLC latency while maintaining overall system stability
Data Source
AI summary
A method, user equipment (UE), and terminal are disclosed, the method includes receiving a first physical downlink shared channel (PDSCH), receiving a second PDSCH that overlaps in time with the first PDSCH, determining a delay in processing time for a hybrid automatic repeat request (HARD)-acknowledgement (ACK) corresponding to the second PDSCH based on the overlapping time between the first PDSCH and the second PDSCH, and transmitting the HARQ-ACK corresponding to the second PDSCH.