Question: In MBMS (Multimedia Broadcast Multicast Service) user data flow synchronization, what is the primary purpose of the timestamp included in SYNC PDU packets sent by the BM-SC (Broadcast Multicast Service Center) to eNBs (evolved Node Bs)?
Option 1: To indicate the arrival time of data at the BM-SC
Option 2: To specify the Maximum Transmission Delay from the BM-SC to the farthermost eNB
Option 3: To notify eNBs of changes in the MBMS service schedule
Option 4: To inform eNBs of the timing for synchronized radio interface transmission based on a common time reference
Explanation: The timestamp in SYNC PDU packets is crucial for synchronizing the radio interface transmission across cells controlled by different eNBs, providing a relative time value tied to the start time of the synchronization period, enabling eNBs to coordinate their MBMS data transmissions over the air interface based on a common time reference.