HARQ Buffer Flush on Configured Grant Deactivation
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Solution Overview
Problem
In wireless communication systems, particularly in 5G NR, there are challenges with hybrid automatic repeat request (HARQ) process handling when a configured sidelink grant is deactivated, leading to pending transport blocks (TBs) being unable to perform retransmissions without new dynamic grants, resulting in resource wastage and increased latency.
Innovation Solution
The proposed solution involves the user equipment (UE) receiving a DCI command to deactivate a sidelink configured grant, where it can either immediately flush the HARQ buffer, send an indication to the network for pending retransmissions, or retransmit pending TBs before clearing the grant, thereby managing resource utilization and latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the configured grant is deactivated without handling pending HARQ processes, then resource configuration flexibility is improved, but pending transport blocks cannot perform retransmissions resulting in resource wastage and increased latency
Solution Approach 1:
The patent applies preliminary action by allowing the UE to retransmit pending transport blocks a certain number of times (e.g., 2 times) before the configured grant is fully deactivated. This preliminary retransmission action ensures that critical data can still be resent successfully before the resource configuration changes, thereby reducing latency while maintaining the ability to adapt resource configuration when needed.
Solution Approach 2:
The patent implements dynamics by introducing a dynamic transition period during grant deactivation. Instead of immediate deactivation, the system dynamically adjusts the grant status to allow limited retransmissions (controlled by a counter parameter) before final deactivation. This dynamic approach balances resource flexibility with reliable data transmission, preventing resource wastage while reducing latency.
2Productivity
If the configured grant is deactivated immediately, then resource utilization is improved, but pending TBs are stuck in buffers without action
Solution Approach 1:
The patent applies preliminary action by enabling the UE to perform retransmissions (e.g., 2 retransmission attempts) before the configured grant is completely deactivated. This ensures that pending transport blocks have multiple opportunities for successful transmission before resources are reallocated, thereby maintaining retransmission reliability while still improving overall resource utilization through timely deactivation.
Solution Approach 2:
The patent maintains continuity of useful action by allowing the configured grant to remain active for a limited period after deactivation is triggered, specifically to complete retransmission of pending transport blocks. This continuous action ensures that resources are not prematurely released, preventing data loss while enabling efficient resource utilization once retransmissions are complete or failed.
3Reliability
If retransmissions are allowed before grant deactivation, then retransmission reliability is improved, but resource configuration flexibility is reduced
Solution Approach 1:
The patent implements dynamics by creating a phased deactivation process where the grant transitions from fully active to partially restricted. During this transition, the UE can perform a limited number of retransmissions (controlled by a counter parameter, e.g., 2 times) before the grant is fully deactivated. This dynamic approach ensures reliable retransmissions while maintaining resource configuration flexibility for other purposes once the transition completes.
Solution Approach 2:
The patent applies preliminary action by allowing retransmissions to occur in advance of complete grant deactivation. The system proactively enables these limited retransmissions during the transition period, ensuring data reliability before resources are reallocated. This preliminary retransmission phase balances reliability requirements with the need for adaptable resource configuration.
4Loss of time
If multiple retransmission attempts are made before deactivation, then loss of time is reduced, but device complexity increases
Solution Approach 1:
The patent implements dynamics by introducing a dynamic counter mechanism that tracks the number of retransmission attempts (e.g., up to 2 attempts) before grant deactivation. This dynamic counter provides a simple, programmable way to control retransmission behavior, reducing latency through multiple attempts while avoiding complex decision-making logic. The counter-based approach maintains device simplicity while achieving reliable timely retransmissions.
Data Source
AI summary
According to some embodiments, a method performed by a wireless device for deactivating a sidelink configured grant comprises: receiving an indication to deactivate a sidelink configured grant; and flushing one or more hybrid automatic repeat request (HARQ) buffers of one or more pending HARQ processes containing one or more transport blocks (TBs) that are being transmitted/retransmitted using the configured sidelink grant.