Question: In UTRA TDD, what is the primary event marking the end of the handover interruption time for a User Equipment (UE) during a handover process?
Option 1: Receipt of the first TTI containing a transport block on the new DPCH
Option 2: Start of UE transmission of the new uplink Dedicated Physical Channel (DPCH)
Option 3: Completion of the last TTI transmission on the new downlink DPCH
Option 4: Initiation of the Random Access Procedure on the new cell
Explanation: The handover interruption time concludes when the UE begins transmitting on the new uplink DPCH, marking the transition from the old channel to the new one and signifying the end of the interruption period.