Question: What happens when a Downlink (DL) data frame arrives at the Node B before the specified Time of Arrival Window Startpoint (TOAWS) in UTRAN's Iub interface NBAP signalling?
Option 1: The data frame is processed immediately, and no additional control frames are sent.
Option 2: A Timing Adjustment Control frame response is triggered to adjust the transmission timing.
Option 3: The data frame is buffered until TOAWS is reached before processing.
Option 4: The data frame is discarded due to premature arrival.
Explanation: If a DL data frame arrives before the specified TOAWS, it indicates a timing mismatch. In response, a Timing Adjustment Control frame is sent to adjust the transmission timing, ensuring synchronization between expected and actual arrival times of data frames, which is crucial for maintaining efficient and synchronized data transfer in wireless networks.