Question: In a TDD (Time Division Duplex) system, as per 3GPP specifications, what is the maximum allowed time for a User Equipment (UE) to complete cell re-selection and send a CELL UPDATE message with cause "cell reselection" in the new cell?
Option 1: Less than 8 seconds
Option 2: Exactly 10 seconds
Option 3: More than 12 seconds but less than 15 seconds
Option 4: Up to 20 seconds for initial attachment, then less than 5 seconds for subsequent re-selections
Explanation: The correct answer is based on the requirement that the cell re-selection delay, defined from the start of time period T2 to when the UE camps on a new cell (Cell 2) and initiates sending a CELL UPDATE message, shall be less than 8 seconds. This ensures efficient handover and minimizes service interruption for the user, highlighting the importance of timely resource management in wireless communications.