L1/L2 Triggered Mobility Configuration for Inter-gNB Handover
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Solution Overview
Problem
Existing 5G wireless communication systems face challenges in managing increased communication traffic and efficiently handling mobility between different base stations, leading to increased interruption times during handover processes due to the limitations of Layer 3-based handovers.
Innovation Solution
The implementation of Layer 1/Layer 2 Triggered Mobility (LTM) to facilitate seamless handovers between different base stations by using unique LTM candidate configuration identification information and coordinated signaling between source and target base stations, enabling efficient inter-gNB-CU mobility without RRC reconfiguration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Layer 3-based handovers are used for mobility between base stations, then the handover process can be managed through existing protocols, but the handover interruption time increases
Solution Approach 1:
The patent applies preliminary action by pre-configuring LTM candidate cells and their associated configurations at the target base station before the actual handover occurs. The source base station requests LTM candidate configurations from the target base station in advance, and the UE is pre-configured with multiple candidate cell information and configurations. This allows the handover to be executed rapidly without requiring time-consuming RRC reconfiguration during the handover process itself, thus reducing handover interruption time while maintaining reliability.
Solution Approach 2:
The patent segments the handover process into multiple independent components: LTM candidate cell identification, configuration preparation, UE capability indication, and actual handover execution. By segmenting the handover into these discrete phases with parallel processing capabilities, the system can prepare configurations in advance while the UE maintains its current connection, enabling faster handover execution without compromising the reliability of the transition.
2Adaptability or versatility
If LTM is extended to inter-different base stations/gNB-CU, then mobility between base stations is enabled, but the configuration complexity increases
Solution Approach 1:
The patent introduces the source base station as an intermediary that manages the complexity of LTM configuration between different base stations. The source base station receives LTM candidate configurations from the target base station, validates them against UE capabilities, and presents simplified LTM configurations to the UE. This intermediary approach allows inter-base station mobility to be enabled while distributing the configuration complexity management across multiple network nodes rather than concentrating it at a single point.
Solution Approach 2:
The patent implements universality by designing a unified LTM configuration framework that can operate both within the same base station (intra-gNB) and between different base stations (inter-gNB). The same basic LTM mechanism, message formats, and configuration procedures are used across different scenarios, with the source base station adapting the configuration based on whether the target is within or outside its control. This multi-functional approach enables inter-base station mobility without requiring entirely separate configuration mechanisms.
3Reliability
If RRC reconfiguration is used for handover, then the handover can be controlled through standard protocols, but the handover speed decreases
Solution Approach 1:
The patent applies preliminary action by performing LTM configuration preparation before the actual handover execution. The target base station provides LTM candidate configurations in advance, and the source base station configures the UE with multiple candidate cell information and configurations prior to triggering handover. When handover is needed, the UE can quickly switch between pre-configured candidates without executing time-consuming RRC reconfiguration procedures, thus achieving high handover speed while maintaining control reliability through the structured configuration approach.
Solution Approach 2:
The patent introduces dynamics by enabling the system to adapt between two operational modes: traditional RRC-based handover for controlled scenarios and LTM-based fast handover for speed-critical scenarios. The UE indicates its LTM capability, and the network dynamically selects the appropriate handover mechanism based on real-time conditions. This dynamic switching capability allows the system to optimize between control reliability and handover speed depending on the specific operational context.
Data Source
AI summary
Disclosed are a method and apparatus for configuring a layer 1 (L1)/layer 2 (L2) triggered mobility (LTM) in a wireless communication system. A source base station transmits a handover request message including an LTM information request to a target base station, receives a handover request acknowledge message including an LTM information response from the target base station, and transmits at least a portion of the received LTM information response to a UE through a radio resource control (RRC) message.