Question: During an LTM cell switch procedure triggered by an LTM Cell Switch Command MAC CE, what action does the UE's MAC entity take if a Timing Advance Command value is received and is not set as FFF (hexadecimal), in the context of a Serving Cell?
Option 1: Ignore the Timing Advance Command and proceed with a random access procedure.
Option 2: Process the received Timing Advance Command but only if associated with a Secondary Cell Group (SCG).
Option 3: Process the received Timing Advance Command, consider the RACH-less LTM cell switch as ongoing, and if applicable, indicate to upper layers to skip the Random Access procedure for this LTM cell switch.
Option 4: Initiate a MAC reset operation before processing the Timing Advance Command.
Explanation: According to the specified behavior for an LTM Cell Switch Command received on a Serving Cell, if the Timing Advance Command value is not set as FFF, the MAC entity processes this command (as per clause 5.2), considers the RACH-less LTM cell switch to be ongoing, and if the MAC entity is associated with SCG, it indicates to upper layers to skip the Random Access procedure for this specific LTM cell switch. This ensures a seamless handover while optimizing the use of network resources by potentially bypassing unnecessary random access procedures in applicable scenarios.