Question: In UTRA TDD, what is the key event marking the end of the Handover Interruption Time for a User Equipment (UE)?
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 containing a transport block on the new DPCH
Option 4: End of the UE's processing of handover commands from the network
Explanation: The Handover Interruption Time is specifically defined as ending when the UE begins transmitting on the new uplink channel, which directly aligns with the initiation of transmission on the new DPCH. This marks the transition to active communication on the new channel, concluding the interruption period.