Question: In a UTRAN (Universal Terrestrial Radio Access Network) environment, what marks the end of the cell re-selection delay period for an FDD (Frequency Division Duplexing) UE (User Equipment)?
Option 1: Receipt of the first broadcast message from the target cell
Option 2: The moment the UE starts sending preambles on the PRACH (Physical Random Access Channel) for a RRC CELL UPDATE message
Option 3: Completion of the handover request to the new cell by the UE
Option 4: Successful decoding of the target cell's system information
Explanation: According to the definition, the cell re-selection delay ends when the UE initiates communication with the new cell for updating its location, specifically marked by sending preambles on the PRACH as part of the process to send a RRC CELL UPDATE message. This action signifies the UE's transition to the new cell is underway, concluding the delay period.