Cell Handover Continuity Using Delayed Source-Cell Release
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Solution Overview
Problem
Conventional handover technologies cause communication interruption in terminal devices due to immediate disconnection from the source serving cell after receiving a handover command, especially when the uplink grant resource of the target serving cell has a large periodicity, leading to communication gaps.
Innovation Solution
The terminal device maintains a connection to the source cell for a specified time period after receiving the handover command and sends information indicating its handover to the target cell, allowing for seamless transition and reducing communication interruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the terminal device immediately disconnects from the source serving cell after receiving the handover command, then the handover process is simplified and faster to initiate, but communication interruption time increases
Solution Approach 1:
The terminal device performs preliminary actions by sending a random access request to the target access network device before actually disconnecting from the source serving cell. This allows the terminal to obtain uplink timing advance information in advance, so that when the handover is completed and uplink resources are allocated, communication can resume immediately without waiting for random access procedures, thus reducing communication interruption time while maintaining simple handover initiation
Solution Approach 2:
The terminal device maintains continuous communication action by keeping the connection to the source serving cell active during the handover preparation phase. Instead of immediately disconnecting, the terminal continues to communicate with the source cell while simultaneously establishing connection with the target cell, ensuring that there is no gap in communication capability and thus eliminating communication interruption
2Loss of time
If the terminal device sends random access request before receiving handover command, then uplink timing advance can be obtained in advance, but the target access network device cannot determine when the terminal is actually handed over
Solution Approach 1:
The terminal device provides feedback to the target access network device by sending indication information that explicitly signals the actual handover completion timing. This feedback mechanism allows the target access network device to understand when the terminal has successfully completed the handover and is ready for uplink communication, thus resolving the information loss problem while maintaining the benefit of early timing advance acquisition
Solution Approach 2:
The indication information sent from the terminal to the target access network device serves as an intermediary signal that bridges the gap between the terminal's internal handover state and the network's understanding of terminal status. This intermediary communication ensures that the target access network device can accurately determine handover completion timing without needing to infer it from the random access request alone
Data Source
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AI summary
This application provides a handover method and apparatus. The method includes: A terminal device receives a handover command from a first access network device, where the handover command instructs the terminal device to be handed over from a first cell to a second cell, the terminal device keeps connected to the first cell within a time range from a first moment to a second moment, the first moment is a moment at which the terminal device receives the handover command, the second moment is later than the first moment, the first access network device is a current serving access network device of the terminal device, and the first cell is a cell served by the first access network device. The terminal device keeps connected to the first cell within the time range from the first moment to the second moment, so that communication interruption time of the terminal device can be reduced.