Question: In UTRAN Iur interface, what is the primary purpose of the Fast Reconfiguration Mode Information Element (IE) sent from the Serving Radio Network Controller (SRNC) to the Drift Radio Network Subsystem (DRNS)?
Option 1: To notify the DRNS to use UE detection on the new configuration as the trigger for reconfiguration timing.
Option 2: To request the DRNS to immediately activate all pending configurations regardless of UE status.
Option 3: To inform the DRNS that the SRNC is switching to a slower reconfiguration mode to prioritize other network tasks.
Option 4: To ask the DRNS to send an acknowledgement for every reconfiguration command before proceeding.
Explanation: The correct answer, Option 1, aligns with the described functionality of the Fast Reconfiguration Mode IE. It highlights the SRNC's intention to synchronize the activation of a new configuration with the moment the User Equipment (UE) is detected on this new setup, optimizing the reconfiguration process in terms of timing and UE experience.