Method, user equipment, and base station for performing early uplink synchronization for l1/l2 triggered mobility

A method for performing, by a user equipment (UE), early uplink (UL) synchronization for layer 1 (L1)/layer 2 (L2)-triggered mobility (LTM), the method comprising:

• receiving, from a base station (BS), a plurality of candidate cell configurations for a plurality of candidate cells, each of the plurality of candidate cell configurations corresponding to a candidate cell of the plurality of candidate cells and indicating whether the UE is to perform an early UL synchronization with the corresponding candidate cell;
• performing, before receiving a cell switch medium access control (MAC) control element (CE), the early UL synchronization with one or more of the plurality of candidate cells in a case that one or more of the plurality of candidate cell configurations corresponding to the one or more of the plurality of candidate cells indicate that the UE is to perform the early UL synchronization;
• receiving, from the BS, the cell switch MAC CE indicating that one of the plurality of candidate cells is a target cell;
• and
• performing, based on the cell switch MAC CE, a cell switching from a source cell to the target cell, wherein, in a case that a candidate cell configuration corresponding to the target cell indicates that the UE is not to perform the early UL synchronization with the target cell:
• the cell switch MAC CE further indicates information for a UL synchronization, and
• the UE performs, based on the information, the UL synchronization with the target cell upon receiving the cell switch MAC CE.

A base station (BS) for performing early uplink (UL) synchronization for layer 1 (L1)/layer 2 (L2)-triggered mobility (LTM), the BS comprising:

• at least one processor;
• and
• at least one non-transitory computer-readable medium coupled to the at least processor and storing one or more computer-executable instructions that, when executed by the at least one processor, cause the BS to:
• transmit, to a user equipment (UE), a plurality of candidate cell configurations for a plurality of candidate cells, each of the plurality of candidate cell configurations corresponding to a candidate cell of the plurality of candidate cells and indicating whether the UE is to perform an early UL synchronization with the corresponding candidate cell;
• and
• transmit, to the UE, a cell switch medium access control (MAC) control element (CE) indicating that one of the plurality of candidate cells is a target cell, wherein:
• the plurality of candidate cell configurations causes the UE to perform, before receiving the cell switch MAC CE, the early UL synchronization with one or more of the plurality of candidate cells in a case that one or more of the plurality of candidate cell configurations corresponding to the one or more of the plurality of candidate cells indicate that the UE is to perform the early UL synchronization,
• the cell switch MAC CE causes the UE to perform, based on the cell switch MAC CE, a cell switching from a source cell to the target cell, and
• in a case that a candidate cell configuration corresponding to the target cell indicates that the UE is not to perform the early UL synchronization with the target cell:
• the cell switch MAC CE further indicates information for a UL synchronization, and
• the cell switch MAC CE causes the UE to perform, based on the information, the UL synchronization with the target cell upon receiving the cell switch MAC CE.