UE-to-UE Relay Reselection and PC5 Link Fallback
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Solution Overview
Problem
Details regarding relay reselection and fallback operations in a UE-to-UE relay scenario have not been specifically discussed in 3GPP 5G wireless systems, affecting the efficiency and reliability of direct communication between user equipments.
Innovation Solution
A first UE selects a relay UE based on relay selection operations, communicates with a second UE via the relay UE, and performs relay reselection or measures the quality of a direct PC5 link, receiving indications from a serving cell to manage relay operations and link quality thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If relay selection operation is performed to enhance coverage, then communication reliability is improved, but system complexity increases
Solution Approach 1:
A relay UE is introduced as an intermediary device between the first UE and second UE to enable communication when direct links are unavailable. The relay UE receives and forwards data packets, acting as a mediator that extends coverage while maintaining communication reliability without requiring complex direct communication protocols between distant UEs.
Solution Approach 2:
The system implements feedback mechanisms where UEs monitor link quality metrics and provide feedback to trigger relay selection or release operations. When link quality falls below thresholds, feedback triggers the network to initiate relay selection procedures, and when quality improves, feedback triggers relay release, enabling dynamic adaptation without constant manual intervention.
2Productivity
If relay reselection operation is implemented, then communication efficiency is improved, but signaling overhead increases
Solution Approach 1:
The relay selection configuration is designed to be dynamic rather than static. The network can update relay selection configurations based on changing channel conditions, and UEs can release relay configurations when no longer needed. This dynamic approach allows the system to adapt to varying communication requirements while managing signaling overhead through conditional updates rather than continuous reconfiguration.
3Reliability
If direct PC5 link quality is monitored, then link reliability is improved, but measurement and processing time increases
Solution Approach 1:
The system performs preliminary actions by establishing relay configurations in advance when direct link quality degrades, rather than waiting for complete link failure. The network proactively selects relay UEs and configures them before communication is completely disrupted, reducing the time needed for reactive recovery operations and minimizing interruption to data transmission.
Data Source
AI summary
Embodiments of the present application relate to methods and apparatuses for relay reselection and fallback operations in a user equipment (UE)-to-UE relay scenario. According to an embodiment of the present application, a user equipment (UE) includes a transceiver and a processor coupled to the transceiver; and the processor is configured to: select a relay UE based on a relay selection operation; communicate with a further UE via the relay UE, wherein the UE and the further UE act as UE-to-UE (U2U) remote UEs; and perform at least one of: receiving a message from the relay UE and performing a relay reselection operation after receiving the message; or measuring quality of a direct PC5 link between the UE and the further UE.