LTM Cell Switch Command Merging TCI State for 5G Mobility
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Solution Overview
Problem
Current wireless communication systems, particularly in 5G NR, face challenges in efficiently performing Layer1/Layer2 Triggered Mobility (LTM) operations due to complexities in beam activation and indication during cell switching, leading to increased latency and signaling overhead.
Innovation Solution
The method involves a User Equipment (UE) and Base Station (BS) that receive and transmit Transmission Configuration Indicator (TCI) state configurations and cell switch commands via MAC Control Elements, allowing the UE to switch between cells while applying appropriate TCI states, even without explicit activation commands, thereby simplifying the LTM process and reducing latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If explicit TCI state activation commands are required before cell switching, then beam configuration reliability is improved, but signaling overhead and processing time increase
Solution Approach 1:
The patent applies preliminary action by pre-configuring TCI state information in the LTM cell switch command MAC CE before the cell switching occurs. The TCI state is included in the activation command received via MAC CE, allowing the UE to have the beam configuration ready in advance. This resolves the contradiction by preparing the beam configuration beforehand, ensuring reliability while reducing the time needed at the moment of switching.
2Loss of time
If TCI state information is included in LTM cell switch command MAC CE, then signaling overhead is reduced, but complexity of MAC CE structure increases
Solution Approach 1:
The patent merges the TCI state information with the LTM cell switch command MAC CE by including the TCI state as part of the same MAC CE structure. Instead of sending separate MAC CEs for cell switching and TCI state activation, the invention combines both functions into a single MAC CE, reducing signaling overhead while managing complexity through integrated design.
Solution Approach 2:
The LTM cell switch command MAC CE is designed to serve multiple functions: indicating the target cell for switching and simultaneously providing the TCI state information for beam configuration. This multi-functionality reduces the need for separate signaling messages, thereby reducing overall signaling overhead while the MAC CE structure handles both purposes efficiently.
3Measurement precision
If separate TCI state activation command is sent before LTM cell switch command, then beam configuration accuracy is improved, but latency in cell switching increases
Solution Approach 1:
The patent combines the TCI state information and the LTM cell switch command into a single MAC CE message. By merging these two previously separate signaling elements, the invention eliminates the sequential timing requirement, allowing the UE to receive both the cell switch command and TCI state configuration simultaneously, thus reducing latency while maintaining configuration accuracy.
Solution Approach 2:
The TCI state information is prepared and included in the LTM cell switch command MAC CE in advance, before the actual cell switching occurs. This preliminary inclusion of beam configuration data ensures that when the UE receives the command, both the cell switching and beam configuration information are available immediately, maintaining accuracy while minimizing the time delay.
Data Source
AI summary
A method for a User Equipment (UE) for performing a Layer1/Layer2 Triggered Mobility (LTM) operation is provided. The UE receives a target Transmission Configuration Indicator (TCI) state configuration and an LTM cell switch command indicating a target cell. The UE switches from the source cell to the target cell and applies a TCI state in the target cell. The TCI state is associated with the target TCI state configuration. The LTM cell switch command indicates the TCI state among a first set of TCI states in a case that the UE receives an LTM TCI state activation command. The LTM cell switch command indicates the TCI state among a second set of TCI states and activates the TCI state in a case that the UE does not receive the LTM TCI state activation command. The first set of TCI states is a subset of the second set of TCI states.