Method and apparatus for cell switching operations

A User Equipment (UE) for cell switching operations, the UE comprising:

• at least one processor;
• and
• at least one non-transitory computer-readable medium coupled to the at least one processor and storing one or more computer-executable instructions that, when executed by the at least one processor, cause the UE to:
• receive one or more Timing Advance Group (TAG) Identities (IDs) from a source serving cell, the one or more TAG IDs associated with one or more candidate target serving cell configurations of one or more candidate target serving cells;
• receive one or more Time Alignment Timers (TATs) from the source serving cell, each TAT of the one or more TATs associated with a respective TAG ID of the one or more TAG IDs;
• receive a Medium Access Control (MAC) Control Element (CE) from the source serving cell, the MAC CE indicating to the UE to switch to a target serving cell, the target serving cell being a candidate target serving cell of the one or more candidate target serving cells and being associated with a TAT of the one or more TATs;
• switch from the source serving cell to the target serving cell in response to receiving the MAC CE;
• and
• keep the TAT associated with the target serving cell running after receiving the MAC CE.

A Base Station (BS) for managing cell switching operations of a User Equipment (UE), the BS comprising:

• at least one processor;
• and
• at least one non-transitory computer-readable medium coupled to the at least one processor and storing one or more computer-executable instructions that, when executed by the at least one processor, cause the UE to:
• configure the UE with one or more Timing Advance Group (TAG) Identities (IDs), the one or more TAG IDs associated with one or more candidate target serving cell configurations of one or more candidate target serving cells;
• configure the UE with one or more Time Alignment Timers (TATs), each TAT of the one or more TATs associated with a respective TAG ID of the one or more TAG IDs;
• and
• transmit a Medium Access Control (MAC) Control Element (CE) to the UE, the MAC CE indicating to the UE to switch to a target serving cell, the target serving cell being a candidate target serving cell of the one or more candidate target serving cells and being associated with a TAT of the one or more TATs,
• wherein the TAT associated with the target serving cell is configured to keep running after the UE receives the MAC CE.