CBG Retransmission Selection Across Configured and Dynamic Grants
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently handling large transport block sizes and low latency requirements, particularly in Extended Reality (XR) traffic, where bursty packet transmissions and frequent retransmissions are common, leading to high capacity demands.
Innovation Solution
A wireless transmit/receive unit (WTRU) employs dynamic and configured resource grants for retransmitting codeblock groups (CBGs) based on feedback, determining the optimal transmission occasion using a delay budget threshold to manage latency and resource allocation efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CBG-based retransmissions are used for large transport blocks, then retransmission efficiency is improved, but latency control becomes more complex due to multiple transmission occasions
Solution Approach 1:
The patent implements dynamic selection between configured grants (CG) and dynamic grants (DG) for CBG retransmissions based on real-time conditions. The WTRU determines whether to use CG or DG resources by evaluating feedback timing, delay budgets, and resource availability, making the retransmission mechanism adaptive rather than static. This dynamic approach allows optimal latency-performance tradeoff adjustments.
Solution Approach 2:
The patent pre-configures multiple PUSCH transmission occasions with configured grants before actual data transmission. These pre-configured resources include multiple opportunities for CBG retransmission within a delay budget, allowing the system to have ready-made resources available when retransmissions are needed, thus reducing decision latency.
2Reliability
If multiple PUSCH transmission occasions are configured for retransmission, then reliability is improved, but resource allocation complexity increases
Solution Approach 1:
The patent segments the retransmission process into distinct phases: configured grant opportunities for initial retransmission attempts, and dynamic grant opportunities for alternative retransmission. Each segment has specific rules for selection, making the overall complex resource allocation manageable through structured division of responsibilities between different grant types.
Solution Approach 2:
The patent implements feedback mechanisms where the WTRU receives HARQ feedback indicating which CBGs were successfully received and which need retransmission. This feedback drives the selection of appropriate transmission occasions and grant types, creating a closed-loop system that adapts resource allocation based on actual transmission outcomes rather than using fixed complex allocation rules.
3Productivity
If dynamic grants are used for CBG retransmission, then resource utilization is improved, but timing synchronization becomes more difficult
Solution Approach 1:
The patent allows dynamic switching between configured grants with fixed timing and dynamic grants with flexible timing based on scheduling decisions. The WTRU can select DG resources when they provide better timing alignment or resource availability, making the system adaptable to varying timing requirements while maintaining efficient resource utilization.
Solution Approach 2:
The patent changes the timing parameter of retransmission based on the grant type selected. For configured grants, timing is fixed according to pre-configured patterns. For dynamic grants, timing is determined by the scheduling decision, allowing flexibility in timing parameters to achieve better synchronization when needed while maintaining efficient resource usage.
Data Source
AI summary
A wireless transmit/receive unit (WTRU) may receive configuration information. The WTRU may transmit a plurality of codeblock groups (CBGs) corresponding to one or more protocol data units (PDUs) of a first PDU set. The WTRU may receive feedback indicating that at least one of the plurality of CBGs of the first PDU set was not successfully received. The WTRU may determine that dynamic PUSCH resource grants are later in time than a second PUSCH transmission occasion. The WTRU may determine whether to retransmit the at least one of the plurality of CBGs of the first PDU set using the dynamic PUSCH resource grants or using the second PUSCH transmission occasion. The determination may be based on an amount of time remaining in a delay budget for the first PDU set. The WTRU may retransmit the at least one of the plurality of CBGs of the first PDU set.