Extended HARQ-ACK Feedback Format for URLLC
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Solution Overview
Problem
In ultra-reliable low latency communications (URLLC), existing HARQ processes face challenges in efficiently managing feedback resources, leading to high overhead and reduced reliability due to the need for extended HARQ-ACK information for all processes, even when only a subset is unsuccessful, which is inefficient and may fail to meet latency constraints.
Innovation Solution
The HARQ-ACK information is split into two sets, with a first set containing regular ACK/NACK information for all processes and a second set providing extended HARQ-ACK information only for a limited number of unsuccessful processes, allowing for configurable reporting and dynamic resource allocation to optimize resource consumption and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If extended HARQ-ACK information is provided for all processes, then reliability of feedback is improved, but overhead increases and resource efficiency deteriorates
Solution Approach 1:
The HARQ-ACK information is segmented into two distinct sets: a first set containing regular ACK/NACK information for all processes, and a second set containing extended HARQ-ACK information only for a limited number of unsuccessful processes. This segmentation allows the system to maintain feedback reliability for critical unsuccessful transmissions while reducing overall overhead by excluding successful transmissions from the extended information set.
Solution Approach 2:
Different parts of the feedback message have different qualities: the first set provides universal ACK/NACK status for all HARQ processes, while the second set provides detailed extended information only locally for unsuccessful processes. This local quality approach ensures that extended information is provided only where needed, optimizing the balance between reliability and overhead.
2Reliability
If extended HARQ-ACK information is provided for all processes, then decoding reliability is improved, but latency increases due to resource allocation requirements
Solution Approach 1:
By segmenting the feedback into two sets, the system can process the first set quickly for all processes while only allocating additional resources for the second set when needed. This reduces the average processing time and latency compared to always processing extended information for all processes, while maintaining decoding reliability when extended information is required.
Solution Approach 2:
The system provides extended HARQ-ACK information partially - only for the limited number of unsuccessful processes rather than all processes. This partial action approach ensures that decoding reliability is maintained for critical cases while avoiding the latency penalty of processing extended information for all processes unnecessarily.
3Ease of manufacture
If fixed HARQ-ACK codebook size is used, then implementation simplicity is improved, but resource efficiency deteriorates when few processes need extended information
Solution Approach 1:
The feedback structure is segmented into a first set that can be accommodated in a fixed codebook for all processes, and a second set that is dynamically activated only when needed. This allows the system to maintain implementation simplicity through the fixed portion while achieving resource efficiency through the conditional activation of the extended information portion.
Solution Approach 2:
The HARQ-ACK codebook transitions from a static fixed size to a dynamic structure where the second set of extended information is conditionally included based on the number of unsuccessful processes. This dynamic approach allows the system to adapt the feedback size to actual needs, optimizing resource consumption while maintaining implementation simplicity through standardized processing of the first set.
Data Source
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AI summary
Various communication systems may benefit from the appropriate selection of feedback mechanisms. For example, ultra-reliable low latency communication systems may benefit from properly formatted extended/super hybrid automatic repeat request acknowledgment feedback. A method caninclude transmitting data of one or more downlink hybrid automatic repeat request processes to a user equipment. The method can also include receiving hybrid automatic repeat request acknowledgment information from the user equipment containing a first set of hybrid automatic repeat request acknowledgment information and a second set of hybrid automatic repeat request acknowledgment information.