Uplink Synchronization Management for Wireless Handover Interruption
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Solution Overview
Problem
Current communication systems face challenges in reducing interruption times during handovers between cells, particularly due to the complexity of maintaining connections and acquiring uplink synchronization, which can lead to increased interruption times and complexity for terminals.
Innovation Solution
A method and apparatus for a terminal to perform a random access procedure before handover, acquiring uplink synchronization in advance by receiving configuration information from a centralized unit, performing layer 1 measurements, and applying synchronization to a target cell, while maintaining connection with the source cell to minimize interruption times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the terminal performs random access procedure after handover to acquire uplink synchronization, then the handover procedure is simple, but the interruption time increases and data loss occurs
Solution Approach 1:
The terminal performs the random access procedure and acquires uplink synchronization with the target cell before the handover is completed. Specifically, the terminal transmits a random access preamble to the target cell and receives a timing advance command in advance, so that when handover occurs, uplink synchronization is already established, eliminating the need for post-handover random access and reducing interruption time
2Loss of time
If the terminal maintains connection with source cell and performs synchronization in advance, then interruption time is reduced, but terminal complexity increases
Solution Approach 1:
The terminal performs preliminary actions by transmitting random access preamble and receiving timing advance command before handover, establishing uplink synchronization in advance. This allows the terminal to maintain connection with the source cell while preparing for handover, reducing interruption time without requiring complex dual-active protocol stack operations
Solution Approach 2:
The terminal autonomously determines the timing advance value by receiving it from the target cell in advance through the random access procedure, and applies it immediately upon handover. This self-service approach eliminates the need for complex coordination with the source cell and reduces terminal complexity compared to DAPS handover
3Loss of time
If RACH-less handover is used to reduce interruption time, then the handover is fast, but it is limited to scenarios where timing advance value is the same or zero
Solution Approach 1:
The terminal performs random access procedure in advance to acquire timing advance value before handover. This preliminary acquisition of timing advance information enables the terminal to perform RACH-less handover in all scenarios, not just when timing advance is the same or zero, thereby expanding the applicability while maintaining fast handover performance
Data Source
AI summary
A method of a terminal may comprise: receiving, from a CU of a base station, configuration information of one or more candidate cells and configuration information for measurement; performing L1 measurement on the candidate cells based on the configuration information for measurement; acquiring uplink synchronization for the candidate cells by performing an uplink synchronization management procedure for the candidate cells based on the configuration information of the candidate cells; reporting a result of the L1 measurement to a DU of the base station; receiving, from the DU of the base station, information on a target cell, being the target cell to switch among the candidate cells, based on the result of the L1 measurement; and applying the uplink synchronization acquired through the uplink synchronization management procedure to the target cell.