Methods and apparatuses of supporting subsequent ltm

A source distributed unit (DU), comprising:

• at least one memory;
• and
• at least one processor coupled with the at least one memory and configured to cause the source DU to:
• determine a candidate cell configuration and an index of the candidate cell configuration for each candidate cell of one or more candidate cells;
• transmit, to a user equipment (UE), a first message indicating the candidate cell configuration and the index of the candidate cell configuration for each candidate cell;
• transmit, to a central unit (CU), a second message indicating the candidate cell configuration and the index of the candidate cell configuration for each candidate cell;
• and
• provide, to a candidate DU, the index of candidate cell configuration for each candidate cell.

A method performed by a central unit (CU), the method comprising:

• determining a candidate cell configuration and an index of the candidate cell configuration for each candidate cell of one or more candidate cells, wherein the index of the candidate cell configuration for each candidate cell is generated by the CU, or received from a source distributed unit (DU), or from a candidate DU;
• transmitting, to a user equipment (UE) via the source DU, a first message indicating the candidate cell configuration and the index of the candidate cell configuration for each candidate cell;
• transmitting, to a source DU, a second message indicating the index of the candidate cell configuration for each candidate cell;
• and
• transmitting, to a candidate DU, a third message indicating the index of the candidate cell configuration for each candidate cell.

A user equipment (UE), comprising:

• at least one memory;
• and
• at least one processor coupled with the at least one memory and configured to cause the UE to:
• receive a message indicating a candidate cell configuration and an index of the candidate cell configuration for each candidate cell;
• perform an L1/L2-Triggered mobility (LTM) cell switch based on the message;
• and
• maintain the candidate cell configuration and the index of the candidate cell configuration for each candidate cell after the LTM cell switch.