Uplink Timing Alignment for Low-Interruption 5G Cell Switching
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Solution Overview
Problem
Current mobility mechanisms in 5G wireless communication systems, such as L3 measurements and RRC signaling, result in high latency, overhead, and service interruption during cell changes, necessitating a more efficient uplink transmission timing management.
Innovation Solution
The method involves receiving an RRC reconfiguration message, a DL control message, and performing a set of operations including applying a TA command for a specific TAG and starting a TA timer, which are executed after a MAC reset during an LTM cell switch command.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If L3 measurements and RRC signaling are used for serving cell change, then mobility management is achieved, but latency and service interruption time increase
Solution Approach 1:
The patent segments the mobility management process into two distinct mechanisms: L3 measurements/RRC signaling for conventional cell changes, and L1/L2 triggered mobility for fast beam switching. This segmentation allows each mechanism to operate independently for its specific use case, enabling fast mobility when conditions permit while maintaining reliability through the conventional path when needed.
Solution Approach 2:
The patent implements preliminary action by performing MAC reset and applying TA commands before the actual cell switch occurs during L1/L2 triggered mobility. The terminal prepares the uplink timing alignment in advance, so when the cell switch is triggered, the terminal can immediately transmit uplink signals without waiting for timing alignment, thereby reducing interruption time.
2Adaptability or versatility
If conventional serving cell change procedures are used, then cell switching is achieved, but overhead and interruption time increase
Solution Approach 1:
The patent extracts the timing alignment function from the cell switch procedure by applying TA commands independently before the switch occurs. This extraction allows the cell switching mechanism to operate without being burdened by the complexity of simultaneous timing alignment, reducing overhead while maintaining adaptability for different cell switch scenarios.
3Speed
If uplink transmission timing is not adjusted during LTM procedure, then cell switch speed is maintained, but uplink synchronization is lost
Solution Approach 1:
The patent applies preliminary action by adjusting uplink transmission timing through TA commands before the LTM cell switch occurs. This preliminary timing adjustment ensures that when the cell switch happens at high speed, the terminal maintains uplink synchronization with the target cell without requiring additional timing alignment procedures afterward.
Data Source
AI summary
A method and an apparatus for managing uplink transmission timing in conjunction with LTM operations is provided. The method comprises specific set of MAC CEs to update the uplink transmission timing of a specific TAG at a specific point of time. The terminal determines the specific TAG and the specific point of time based on the type of MAC CE containing the TAC and the contents contained within the MAC CE.