Question: During a satellite switch with re-synchronization in RRC_CONNECTED state, what action does the User Equipment (UE) take regarding its uplink (UL) synchronization after being informed by the `SatSwitchWithReSync` message?
Option 1: The UE immediately regains UL synchronization with the source satellite without any additional steps.
Option 2: The UE informs lower layers that UL synchronization is lost due to the satellite switch and then starts the process to re-synchronize.
Option 3: The UE pauses timer T430 until UL synchronization with the new satellite is confirmed.
Option 4: The UE ignores the `SatSwitchWithReSync` message for UL synchronization purposes.
Explanation: When a satellite switch with re-synchronization occurs in the RRC_CONNECTED state, the UE must acknowledge the loss of UL synchronization as part of the handover process. This involves notifying lower layers about the loss (to manage expectations and handle potential data interruptions) before initiating the re-synchronization process with the new satellite (SpCell). This step ensures a controlled transition, minimizing data loss and service disruption. The correct sequence includes informing about the loss and then working to re-establish synchronization, making Option 2 the accurate choice.