RRC Reconfiguration Sync for Relay Handover Continuity
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Solution Overview
Problem
During path switching from direct to indirect communication in wireless communication systems, issues arise when the target relay UE device is in the RRC IDLE or RRC INACTIVE state, leading to potential failures in RRC establishment and inter-cell coordination challenges.
Innovation Solution
A base station transmits an RRC Reconfiguration Message with Sync to a remote UE device, identifying a target relay UE device and explicitly or implicitly specifying a cell for reselection. The remote UE device determines if the target relay UE device is connected to the cell and sends a message to the base station if handover is not possible.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the target relay UE device is in RRC IDLE or RRC INACTIVE state, then the remote UE device can potentially connect via indirect path, but RRC establishment fails and inter-cell coordination becomes challenging
Solution Approach 1:
The base station performs preliminary actions by transmitting an RRC Reconfiguration Message with Sync to the remote UE device before the actual path switch, explicitly or implicitly identifying a target cell for reselection. This preparatory configuration ensures that when the relay UE device transitions from RRC IDLE/INACTIVE to connected state, the RRC establishment can proceed successfully without failure.
Solution Approach 2:
The patent introduces an intermediary mechanism where the base station acts as a mediator between the remote UE device and the target relay UE device. The base station coordinates the path switching process by providing synchronization information and target cell identification, enabling seamless inter-cell coordination even when the relay UE device is in RRC IDLE or INACTIVE state.
2Reliability
If the base station explicitly identifies a target cell for reselection, then inter-cell coordination is improved, but the complexity of the RRC reconfiguration message increases
Solution Approach 1:
The patent applies local quality by making the target cell identification explicit only when necessary for inter-cell coordination, while allowing implicit identification in scenarios where the source cell is already the target cell. This selective approach improves inter-cell coordination reliability without unnecessarily increasing RRC message complexity in all cases.
Solution Approach 2:
The patent changes the parameter of target cell identification from always explicit to conditionally explicit or implicit based on whether inter-cell coordination is required. This parameter change optimizes the balance between coordination reliability and message complexity by adapting the identification method to the specific switching scenario.
Data Source
AI summary
In the examples described herein, a base station transmits, to a remote UE device over a direct Uu communication link, an RRC Reconfiguration Message with Sync identifying a target relay UE device and explicitly or implicitly identifying a cell for reselection by the target relay UE device. The identified cell is provided by the base station, and the remote UE device is connected to the cell. The remote UE device receives, from the target relay UE device, a discovery message. Based at least partially on the discovery message, the remote UE device determines whether the target relay UE device is connected to the cell. In response to determining that the target relay UE device is not connected to the cell, the remote UE device transmits, to the base station over the direct Uu communication link, a message indicating that handover to the target relay UE device is not possible.