MCG Failure Reporting During 5G NR DAPS Handover
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Solution Overview
Problem
The existing 3GPP 5G New Radio (NR) system lacks a clear solution for the coexistence issue of dual active protocol stack (DAPS) handover procedures and radio link failure (RLF) report mechanisms for master cell groups (MCGs, particularly during DAPS handover procedures.
Innovation Solution
Implementing a method and apparatus for wireless communications that include configuring a timer for fast MCG link recovery, initiating MCG failure information procedures based on specific timers and conditions during DAPS handover, and transmitting RLF reports to manage RLFs effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a UE performs RRC re-establishment procedure upon RLF during DAPS handover, then connection reliability is improved, but handover continuity and user experience deteriorate due to unnecessary re-establishment when source link recovery is possible
Solution Approach 1:
The network configures the UE with a fast MCG link recovery timer (T316) before handover occurs. When RLF is detected during DAPS handover, the UE checks if T316 is running. If it is, the UE suppresses RRC re-establishment and waits for potential source link recovery, avoiding unnecessary connection interruption while maintaining reliability through timer-based control
Solution Approach 2:
The system dynamically adjusts UE behavior based on timer state. The UE monitors the running state of T316 and adaptively changes its response to RLF: suppressing re-establishment when T316 is running (recovery in progress), but allowing it when T316 is not running (no recovery expected). This dynamic adaptation resolves the contradiction between reliability and continuity
2Productivity
If the UE suppresses RRC re-establishment when T316 is running, then handover continuity is improved, but connection reliability may worsen if source link recovery fails
Solution Approach 1:
The network provides feedback through the T316 timer state to the UE. When the network determines source link recovery is attempted, it starts T316 and informs the UE (implicitly through configuration). The UE uses this feedback to suppress re-establishment. If recovery fails and T316 expires, the feedback mechanism allows the UE to retry or fall back, maintaining reliability while preserving continuity during the recovery attempt window
Solution Approach 2:
The system prepares a fallback mechanism by configuring T316 with an appropriate timeout value before handover. This cushioning timer allows the UE to wait for source link recovery without committing to permanent suppression of re-establishment. If recovery fails within the cushioning period, the UE can still initiate re-establishment, thus protecting reliability while enabling continuity during the cushioning window
3Loss of information
If the network monitors RLF reports from UEs during DAPS handover, then network optimization is improved, but signaling overhead and processing complexity increase
Solution Approach 1:
The RLF report mechanism is activated locally only for UEs undergoing DAPS handover, not for all UEs. The network identifies DAPS handover UEs through specific configuration messages and applies enhanced monitoring only to this subset. This localized approach captures necessary optimization information for DAPS scenarios without imposing universal signaling overhead, thus improving network optimization while controlling processing complexity
Solution Approach 2:
The patent extracts and isolates the RLF reporting requirement specifically for DAPS handover scenarios from the general RLF reporting mechanism. By separating DAPS-specific reporting from universal reporting, the network can process DAPS RLF reports through specialized handling procedures, reducing the complexity burden on general signaling processing while still capturing valuable optimization information for DAPS handover optimization
Data Source
AI summary
Embodiments of the present application relate to a method and an apparatus for a master cell group, e.g., a dual active protocol stack (DAPS) handover procedure and a radio link failure (RLF) report mechanism associated with a source link during the DAPS handover procedure under a 3rd Generation Partnership Project (3GPP) 5G New Radio (NR) system or the like. According to an embodiment of the present application, a method can include: receiving configuration information including a timer associated with fast MCG link recovery; receiving a radio resource control (RRC) reconfiguration message including DAPS configuration information; in response to a RLF of a source link for a MCG, initiating a MCG failure information procedure based on the condition that the timer for handover is running or not. In addition, a RLF-report may be reported to a target cell after a UE successfully accesses to the target cell.