Question: In a UTRAN TDD environment, what is the maximum allowed interruption time for a UE that has synchronized to a GSM cell before receiving a HANDOVER FROM UTRAN COMMAND?
Option 1: Less than 40 ms
Option 2: Exactly 50 ms
Option 3: Up to 100 ms
Option 4: Greater than 200 ms
Explanation: This requirement is crucial for ensuring seamless handovers between different network types (UTRAN to GSM in this case), minimizing service interruption. The specified time of less than 40 ms is designed to maintain a satisfactory user experience during handover processes, especially in scenarios where the UE has already established synchronization with the target GSM cell before receiving the handover command. This highlights the importance of efficient radio resource management (as referenced by the normative TS 25.123 for TDD) in maintaining high-quality service continuity across heterogeneous networks.