L1/L2 Mobility Time Advance Acquisition
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Solution Overview
Problem
The current 5G new radio (NR) system's serving cell change process, which involves complete L2 and L1 resets, results in longer latency, higher overhead, and longer interruption times during user equipment (UE) movement between coverage areas, compared to beam switch mobility.
Innovation Solution
Implementing L1/L2 mobility enhancements that allow serving cell changes via L1/L2 signaling, where some L2/L1 configuration of non-serving cells is included in current RRC configurations before handover, enabling the acquisition and maintenance of time advance (TA) of non-serving cells to reduce latency and overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a serving cell change is performed through complete L2 and L1 resets with RRC signaling, then the handover is reliable and complete, but the latency and interruption time increase significantly
Solution Approach 1:
The patent performs TA acquisition and maintenance for non-serving cells in advance, before the actual handover occurs. By pre-configuring L2/L1 parameters and maintaining TA values for candidate target cells during the current serving cell connection, the UE is prepared for rapid cell switching without needing to perform complete L2/L1 resets during handover, thus reducing latency while ensuring reliability
Solution Approach 2:
The patent segments the handover process into distinct phases: TA acquisition phase (before handover), TA maintenance phase (during handover preparation), and execution phase (actual cell switching). This allows the L2/L1 configuration to be partially maintained across cell boundaries, avoiding complete resets and reducing overall handover time while preserving reliability through structured phase transitions
2Stability of the object's composition
If L2/L1 configuration is completely reset during serving cell change, then synchronization is ensured, but overhead and interruption time increase
Solution Approach 1:
The patent makes the L2/L1 configuration universal by designing it to be applicable across multiple cells (serving and non-serving). The same L2/L1 configuration structure is reused for candidate target cells, allowing the configuration to serve multiple functions: maintaining current cell operation and preparing for future handovers. This reduces overhead by avoiding redundant configuration messages while ensuring synchronization stability through consistent configuration structures
Solution Approach 2:
The patent performs L2/L1 configuration in advance for non-serving cells before handover is needed. By pre-configuring these cells with appropriate L2/L1 parameters and maintaining TA values, the system ensures synchronization is already established when handover occurs, eliminating the need for complete resets and reducing both overhead and interruption time
3Measurement precision
If RACH procedure is performed during handover to non-serving cell, then TA is acquired accurately, but latency is introduced
Solution Approach 1:
The patent performs the RACH procedure and TA acquisition in advance, before the actual handover to the non-serving cell. By completing the random access procedure and obtaining accurate TA values during the current serving cell connection, the UE eliminates the need to perform RACH during handover, thus maintaining TA acquisition accuracy while removing the associated latency from the critical handover path
Data Source
AI summary
A method and an apparatus are provided in which a user equipment (UE) connected with a serving cell performs a random access channel (RACH) procedure for a non-serving cell. The UE acquires a time advance (TA) of the non-serving cell based on the RACH procedure. The UE performs an L1/L2-based handover from the serving cell to the non-serving cell with the acquired TA.