Conditional L1/L2 Mobility With Pre-Synchronized Target Cells
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional handover procedures in wireless communication, such as Layer 3 mobility, suffer from high latency, overhead, and interruption time due to incomplete L2 resets and unreliable measurement reporting, leading to increased failure rates, while existing Layer 1/Layer 2 triggered mobility (LTM) improvements in 3GPP Release 18 lack detailed configurations for conditional handover mechanisms.
Innovation Solution
A method and apparatus for a conditional Layer 1/Layer 2 (L1/L2) triggered mobility (LTM) procedure, including UE capability reporting, conditional LTM configuration, and early UL synchronization through Timing Advance (TA)-related information in MAC Control Elements, enabling robust and efficient handover without network signaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Layer 3 handover procedure is used, then handover decision can be made based on measurement reports, but latency and interruption time increase due to complete L2 resets and RRC signaling
Solution Approach 1:
The patent applies preliminary action by performing L2 synchronization and acquiring Timing Advance (TA) information before the actual handover execution. The UE prepares the target cell configuration and completes uplink synchronization in advance, so that when handover is triggered, the UE can immediately switch cells without performing complete L2 resets, thereby reducing handover latency while maintaining reliability
Solution Approach 2:
The patent segments the handover procedure into distinct phases: L1 measurement phase, L2 preparation phase (where TA is acquired and target cell is synchronized), and execution phase. This segmentation allows the time-consuming synchronization and TA acquisition to occur separately before handover, rather than as part of the critical handover path, reducing overall interruption time
2Reliability
If conventional handover with complete L2 resets is performed, then handover can be executed, but overhead and interruption time increase
Solution Approach 1:
The patent performs L2 synchronization and TA acquisition as preliminary actions before handover execution. By the time handover is triggered, the UE already has valid TA information and is synchronized with the target cell, eliminating the need for complete L2 resets during handover and reducing procedural complexity
Solution Approach 2:
The patent extracts the time-consuming L2 synchronization and TA acquisition steps from the critical handover path and performs them in advance. This separation removes the bottleneck from the handover execution phase, reducing both overhead and procedural complexity while ensuring reliable handover completion
3Speed
If LTM is used to reduce latency, then handover speed improves, but detailed configurations for conditional handover are missing
Solution Approach 1:
The patent implements conditional LTM by preparing target cell configurations and acquiring TA information in advance based on predicted handover conditions. When specific conditions are met (such as signal quality thresholds), the pre-prepared configurations are immediately activated, enabling fast handover while managing complexity through conditional triggers
Solution Approach 2:
The patent introduces dynamic conditional configurations where handover parameters and target cell selections adapt based on real-time channel conditions and UE behavior. The system dynamically adjusts which pre-prepared configurations to use based on measured conditions, enabling flexible fast handover without requiring exhaustive preconfiguration for all possible scenarios
4Productivity
If measurement reporting is unreliable or source gNB cannot transmit HO command, then handover decision can be made, but handover failure rate increases
Solution Approach 1:
The patent performs L2 synchronization and TA acquisition in advance as preliminary actions, so that when handover is triggered, the UE is already prepared to immediately access the target cell. This pre-preparation ensures that even if measurement reporting is delayed or HO command transmission fails, the UE can autonomously execute handover using pre-acquired synchronization information, reducing failure rate
Solution Approach 2:
The patent enables the UE to self-service the handover execution by autonomously applying pre-configured target cell parameters and using pre-acquired TA information to immediately access the target cell without waiting for network confirmation. This self-service capability ensures handover continuity even when network signaling is unreliable
Data Source
AI summary
A method for a conditional Layer 1/Layer 2 (L1/L2) triggered mobility (LTM) procedure is provided. The method is implemented by a user equipment (UE) and includes receiving a conditional LTM command from a source base station (BS), wherein the conditional LTM command includes a first target cell configuration of a first target cell and an execution condition. The method includes receiving a first Medium Access Control (MAC) Control Element (CE) associated with the first target cell from the source BS, wherein the first MAC CE includes Timing Advance (TA)-related information. The method includes switching to the first target cell by applying the first target cell configuration and the received TA-related information when the execution condition is fulfilled.