UE Cell Change Activation Time Synchronization
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Solution Overview
Problem
In high-speed user equipment, the link quality of the serving cell may degrade before the HS-DSCH serving cell change procedure to the target cell is completed, leading to call drops due to network controller inability to reach the user equipment.
Innovation Solution
The user equipment calculates and sets an activation time for cell change based on a timing offset received from the network controller, allowing synchronized operation and ensuring the cell change occurs only when approved, thus preventing call drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the HS-DSCH serving cell change procedure is performed in high-speed user equipment, then the user equipment can maintain connection during movement, but the link quality of the serving cell may degrade before the cell change procedure is completed, leading to call drops
Solution Approach 1:
The network controller pre-calculates and signals a timing offset to the user equipment before the actual cell change occurs. This timing offset represents the time required for the cell change procedure, allowing the user equipment to prepare in advance and execute the change at the precise moment when link quality is still adequate, thereby preventing call drops while maintaining reliable connection.
Solution Approach 2:
The solution introduces dynamic timing adjustment by calculating the cell change activation time based on the signaled timing offset and current system state. This dynamic approach allows the cell change to be scheduled at the optimal moment considering the high-speed movement conditions, balancing the need for quick handover with maintaining sufficient link quality throughout the procedure.
2Reliability
If the cell change activation time is not synchronized between user equipment and network controller, then independent operation is simpler, but the cell change may occur at different times causing protocol errors and call drops
Solution Approach 1:
The user equipment feeds back the calculated activation time to the network controller to confirm synchronization. This feedback mechanism ensures that both the user equipment and network controller have a consistent understanding of when the cell change will occur, preventing protocol errors and call drops while maintaining a relatively simple synchronization approach based on the pre-signal ed timing offset.
3Productivity
If the activation time is calculated without considering timing offset, then the calculation is simpler, but the cell change does not occur at the optimal time leading to link quality degradation
Solution Approach 1:
The network controller pre-calculates the timing offset based on system parameters and signals it to the user equipment in advance. This preliminary calculation allows the user equipment to determine the optimal activation time that accounts for processing delays and transmission times, ensuring the cell change occurs at the precise moment when link quality is still sufficient while maintaining simple execution at the user equipment side.
Data Source
AI summary
The present solution relates to a method in a user equipment (310) for setting up an activation time of a cell change of the user equipment (310) from a serving cell (305) to a target cell (308) in a wireless communications network (300). The user equipment (310) receives (501) a timing offset from a network controller (315), calculates (502) a cell change activation time based on the timing offset and transmits (503) the calculated activation time to the network controller (315). Then, the user equipment (310) receives (504) an approval of the cell change from the network controller (315) and moves (505) from the serving cell (306) to the target cell (308) at the activation time if the approval has been received.