Inter-RAT Handover Timer Control for Mobility Robustness
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Solution Overview
Problem
The 3GPP 5G NR technology lacks a detailed Mobility Robustness Optimization (MRO) mechanism for inter-Radio Access Technology (RAT) handover procedures, leading to radio link failures and handover failures during transitions between different radio access technologies.
Innovation Solution
Implement methods and apparatuses for UEs and BSs to manage inter-RAT handovers by receiving and transmitting specific mobility command and RRC release messages, including timers and failure report information, to optimize handover procedures and improve network performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inter-RAT handover procedure is implemented without detailed MRO mechanism, then handover between different radio access technologies can be performed, but radio link failures and handover failures occur frequently
Solution Approach 1:
The patent segments the handover failure analysis by introducing separate timer mechanisms (T310, T312) for different failure scenarios. T310 monitors radio link quality and triggers failure detection, while T312 specifically handles measurement report-based failure recovery. This segmentation allows targeted optimization of specific handover failure modes without requiring a complete redesign of the handover mechanism.
Solution Approach 2:
The patent applies preliminary action by configuring timers T310 and T312 before handover failures occur. These timers are pre-configured with appropriate thresholds and durations to proactively detect potential handover failures before they impact service quality. The network can prepare recovery actions in advance based on timer expirations, rather than reacting after failures occur.
2Reliability
If timer T312 is not stopped during inter-RAT handover, then failure recovery can be initiated based on measurement reports, but handover failures may occur due to conflicting timer operations
Solution Approach 1:
The patent implements dynamic timer management where T312 is conditionally stopped during inter-RAT handover based on the handover command received. The UE dynamically adjusts timer operation states: T312 is stopped when receiving inter-RAT handover commands to prevent conflicts, but continues running for intra-RAT handovers where it remains relevant. This dynamic approach optimizes handover success while maintaining procedural clarity through context-dependent behavior.
3Reliability
If detailed failure reports are transmitted, then network can optimize mobility problems, but signaling overhead increases
Solution Approach 1:
The patent extracts only the essential failure information needed for mobility optimization by having the UE report specific timer expiration events (T310, T312) and associated measurement data. Rather than transmitting complete failure logs, the system extracts key indicators such as failure cause, target cell identity, and measurement results at the time of failure. This selective extraction provides sufficient information for network optimization while minimizing signaling overhead.
Data Source
AI summary
Embodiments of the present application relate to methods and apparatuses for a mobility robustness optimization (MRO) mechanism of an inter-radio access technology (RAT) handover procedure. According to an embodiment of the present application, a method can include: receiving a mobility command message from a source new radio (NR) cell, wherein the mobility command message includes an identifier (ID) of a target cell, and the target cell is at least one of an evolved universal terrestrial radio access network (E-UTRAN) cell and an universal terrestrial radio access network (UTRAN) cell; determining whether a timer for initiating failure recovery based on triggering a measurement report (e.g., timer T312) is running; and in response to the timer being running, stopping the timer. Furthermore, radio link failure report (RLF) information is transmitted to a network in response to the failure of Inter-RAT handover from NR to E-UTRAN and UTRAN.