Uplink Synchronization for Non-Serving Cells to Reduce Handover Latency
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Solution Overview
Problem
Current wireless communication networks face challenges in quickly and efficiently performing handover procedures due to the need for uplink synchronization during the handover process, which can increase latency and failure rates.
Innovation Solution
A UE maintains uplink synchronization with non-serving cells in its candidate set without establishing links with them, allowing for seamless handover to a target cell without requiring additional uplink synchronization during the handover process, thereby reducing latency and improving success rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uplink synchronization is performed during handover, then handover reliability is improved, but handover latency increases
Solution Approach 1:
The UE performs uplink synchronization with the target cell before the handover is actually executed. The synchronization state is maintained in a suspended manner during the handover execution phase, so when handover occurs, the UE can immediately use the pre-established synchronization without performing additional synchronization procedures, thus reducing handover latency while ensuring reliability
2Speed
If uplink synchronization is maintained with all candidate cells, then handover speed is improved, but device complexity increases
Solution Approach 1:
Instead of maintaining full uplink synchronization with all candidate cells uniformly, the UE selectively maintains suspended synchronization states only for cells that are likely handover targets based on measurement reports. This localized approach focuses resources on specific candidate cells rather than all possibilities, reducing overall device complexity while still enabling fast handover when needed
3Reliability
If link is established with non-serving cells, then handover reliability is improved, but resource consumption increases
Solution Approach 1:
The UE creates a suspended copy of the uplink synchronization state from the serving cell and applies it to the target cell during handover, rather than establishing a completely new link. This copying approach reuses existing synchronization information and resource configurations, significantly reducing the energy and resources required compared to establishing fresh links with all candidate cells
Data Source
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AI summary
Techniques for quickly and efficiently performing handover are described. A user equipment (UE) may maintain a link with a serving cell and may communicate with this cell via the established link. The UE may have a candidate set of non-serving cells that are candidates for handover. The UE may maintain uplink synchronization with one or more non-serving cells in the candidate set, without having to maintain links with any of the non-serving cells. The UE may update uplink synchronization with the non-serving cells via an access procedure, e.g., send access probes to the non-serving cells and receive timing adjustments from these cells. One non-serving cell with which the UE has maintained uplink synchronization may be selected as a target cell for handover. The UE may then perform handover from the serving cell to the target cell, without performing uplink synchronization during the handover, which may improve handover latency and success rate.