Grant-Free Uplink Retransmission Timer Mechanism
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Solution Overview
Problem
Grant-free uplink transmissions in communication systems face challenges with low reliability due to random collisions and the lack of acknowledgement feedback, leading to increased latency and reduced reliability when the network entity fails to detect user equipment transmissions.
Innovation Solution
User equipment initiates a timer for grant-free uplink transmissions and re-transmits data packets if no feedback or a negative acknowledgement is received within the timer, allowing for proactive re-transmission and reducing latency and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If grant-free uplink transmissions are used for low latency channel access, then latency is reduced, but reliability deteriorates due to random collisions and lack of acknowledgement feedback
Solution Approach 1:
The network entity proactively transmits an acknowledgement message before the UE would normally assume successful reception. This preliminary action prevents the UE from unnecessarily retransmitting packets, resolving the reliability issue while maintaining the low-latency benefit of grant-free transmissions.
Solution Approach 2:
The system introduces explicit feedback through acknowledgement messages transmitted by the network entity. This feedback mechanism allows the UE to accurately determine whether its grant-free transmission was successful, eliminating the need for conservative retransmission assumptions and improving overall transmission reliability.
2Loss of energy
If no acknowledgement feedback is transmitted for successful GFUT, then network resources are conserved, but latency increases due to false assumption of correct packet reception
Solution Approach 1:
The network entity monitors its own reception status and autonomously decides when to transmit acknowledgement messages. This self-service approach ensures acknowledgements are sent only when necessary (i.e., when the network entity fails to detect the transmission), optimizing network resource usage while preventing false reception assumptions.
Solution Approach 2:
The system implements on-demand feedback where the network entity transmits acknowledgement messages selectively based on whether it detected the UE transmission. This feedback mechanism prevents false reception assumptions without requiring continuous feedback transmission, thus conserving network resources.
3Loss of energy
If the network entity fails to detect UE transmission, then no feedback is transmitted saving resources, but reliability reduces as UE falsely assumes correct packet reception
Solution Approach 1:
The network entity transmits an acknowledgement message when it fails to detect a UE grant-free transmission. This feedback mechanism informs the UE that its transmission was not received, preventing false reception assumptions and unnecessary retransmissions, thereby improving reliability while managing feedback transmission energy.
Solution Approach 2:
The acknowledgement message acts as an intermediary signal that mediates between the network entity's detection failure and the UE's reception assumption. This intermediary feedback ensures the UE has accurate information about transmission status without requiring continuous monitoring or additional complex signaling mechanisms.
4Reliability
If timer-based retransmission mechanism is implemented, then reliability improves through proactive re-transmission, but device complexity increases due to timer management
Solution Approach 1:
The timer mechanism works in conjunction with explicit acknowledgement feedback from the network entity. The UE uses the feedback to determine whether to stop the timer and consider transmission successful, or continue waiting and potentially retransmit. This feedback-driven timer management reduces complexity compared to blind timer-based retransmission schemes.
Data Source
AI summary
A method may include transmitting, by a user equipment, a data packet to a network entity. The method may further include starting, by the user equipment, a timer with a first value associated with the transmission to the network entity. The method may further include checking, by the user equipment, for feedback from the network entity associated with the transmission to the network entity. The method may further include determining, by the user equipment, that no feedback for the transmission has been received within the associated timer, or a negative acknowledgement has been received without the corresponding resource allocation for re-transmission. The method may further include in response to receiving no feedback associated with the transmission within the associated timer, or receiving a negative acknowledgement without the corresponding resource allocation for re-transmission, re-transmitting, by the user equipment, the data packet to the network entity.