Identification-Based L1/L2 Mobility for Inter-gNB-CU Handover

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Solution Overview

Problem

Existing 5G wireless communication systems face challenges in efficiently managing increased communication traffic and supporting inter-base station mobility, particularly in scenarios requiring ultra-reliable and low-latency communications, due to the limitations of current LTM technologies that primarily support intra-gNB-CU mobility, leading to increased interruption times during cell switching.

Innovation Solution

A method and apparatus for performing L1/L2 Triggered Mobility (LTM) that includes comparing identification information values of serving and target cells to determine PDCP reestablishment and L2 reset operations, enabling efficient inter-gNB-CU mobility by defining specific information for PDCP re-establishment and L2 reset, thereby supporting seamless handovers between different base stations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If LTM is used for intra-gNB-CU mobility, then cell switching is efficient, but inter-gNB-CU mobility is not supported leading to increased interruption times

Engineering Contradiction:
Improvecell switching speedVSAvoidinter-gNB-CU mobility support
Core Design Contradiction:
SpeedVSAdaptability or versatility

Solution Approach 1:

The patent segments the mobility management process by introducing separate identification information for PDCP reestablishment and L2 reset operations. This allows independent control of different protocol layers during inter-gNB-CU handovers, enabling efficient mobility while maintaining data integrity across base station boundaries.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent implements dynamic decision-making by comparing identification information values to determine whether PDCP reestablishment and L2 reset are needed. This dynamic approach allows the system to adapt the handover procedure based on specific cell and gNB-CU conditions, optimizing performance for both intra and inter gNB-CU scenarios.

Inventive Principle:
Principle #15Dynamics

2Reliability

If traditional handover procedures are used for inter-gNB-CU mobility, then data integrity can be maintained, but interruption times increase

Engineering Contradiction:
Improvedata integrityVSAvoidinterruption time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The patent performs preliminary comparisons of identification information (serving cell ID vs target cell ID, serving gNB-CU ID vs target gNB-CU ID) before executing the handover. This preliminary action determines the necessary protocol layer operations in advance, allowing the system to prepare PDCP reestablishment and L2 reset operations beforehand, thereby reducing actual interruption time while ensuring data integrity.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent changes the operational state of protocol layers (PDCP and L2) based on parameter comparisons. By dynamically adjusting whether PDCP reestablishment and L2 reset are performed based on identification information matching, the system optimizes the balance between data integrity maintenance and interruption time reduction for inter-gNB-CU handovers.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP4598127A1Method and apparatus for performing LTM (l1/l2 triggered mobility)
Publication Date: 2025.08.06 KT CORP
  • EP4598127A1 patent drawingFigure 1
  • EP4598127A1 patent drawingFigure 2
  • EP4598127A1 patent drawingFigure 3A~3B

AI summary

Disclosed are a method and apparatus for performing layer 1 (L1)/layer 2 (L2) triggered mobility (LTM) in a wireless communication system. The UE performs first comparison between a first identification information value of a serving cell and a second identification information value of a target cell to determine whether to reestablish a packet data convergence protocol (PDCP) in an LTM procedure. In addition, after performing the first comparison in the LTM procedure, the UE performs second comparison between a third identification information value of the serving cell and a fourth identification information value of the target cell to determine whether to reset the L2. Then, the UE performs an L2 reset operation based on the first comparison and the second comparison in the LTM procedure.