Sidelink HARQ Relay Feedback for Extended-Range Groupcast
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Solution Overview
Problem
Existing sidelink hybrid automatic repeat request (HARQ) processes in wireless communication systems face challenges in supporting groupcast communications with extended range, particularly in scenarios where group members are scattered and beyond direct transmission reach, leading to latency and high resource consumption.
Innovation Solution
Integration of UE-to-UE relays into the HARQ process, allowing for a hybrid automatic repeat request process that includes a transmitter UE initiating groupcast transmissions, monitoring feedback from relay and remote UEs at multiple time instances, and generating a retransmission strategy based on this feedback, ensuring backward compatibility with legacy systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If relay user equipment are integrated into the HARQ process for groupcast transmissions, then communication range is extended and reliability is improved, but system complexity and feedback monitoring requirements increase
Solution Approach 1:
Relay user equipment are introduced as intermediary nodes between the transmitter UE and remote UEs. These relays receive transport blocks from the transmitter, monitor feedback from remote UEs, and report to the transmitter, thereby extending communication range and improving reliability without requiring direct long-range transmissions.
Solution Approach 2:
The HARQ feedback monitoring process is segmented into multiple time instances (first time instance for initial feedback, second time instance for relay feedback). This segmentation allows the system to handle feedback from different nodes (remote UEs and relay UEs) separately, managing complexity through structured temporal division.
2Reliability
If feedback is monitored at multiple time instances for relay and remote UEs, then retransmission reliability is improved, but latency and resource consumption increase
Solution Approach 1:
The system performs preliminary feedback monitoring at a first time instance before initiating retransmissions. Relay UEs monitor feedback from remote UEs and prepare their reports in advance. This preliminary action allows the transmitter to make informed retransmission decisions faster, reducing overall latency despite multiple monitoring instances.
Solution Approach 2:
Feedback monitoring occurs at periodic time instances (first time instance and second time instance) rather than continuously. This periodic structure balances reliability requirements with latency constraints by sampling feedback at critical moments in the HARQ process.
3Length of stationary object
If relay user equipment monitor feedback from remote user equipment and report to transmitter, then extended range communication is enabled, but resource consumption and system overhead increase
Solution Approach 1:
Relay UEs act as intermediaries that locally monitor feedback from remote UEs and report only essential information to the transmitter UE. This intermediary function enables extended range communication while consuming fewer resources than if the transmitter directly monitored all feedback or if continuous monitoring was performed.
Data Source
AI summary
A method may include initiating, by a transmitter user equipment, a hybrid automatic repeat request process for groupcasting a transport block over seedbank to one or more relay user equipment and at least one remote user equipment. The method may also include performing a first groupcast transmission of the transport block using the hybrid repeat request process. The method may further include monitoring feedback from the one or more relay user equipment and the at least one remote user equipment at a first time instance and at a second time instance. In addition, the method may include generating a retransmission strategy of the transport block depending on the feedback monitored at the first time instance and the second time instance. Further, the method may include controlling retransmission of the transport block using the hybrid automatic repeat request process based on the retransmission strategy.