Question: In a TDD/FDD handover scenario, what determines whether an inter-frequency FDD target cell is considered "known" by the User Equipment (UE)?
Option 1: The UE's previous successful handovers to the same cell.
Option 2: The UE having measured the target cell during the last 5 seconds.
Option 3: The type of Radio Resource Management (RRM) algorithm employed by the network.
Option 4: The signal strength of the Primary CPICH (Common Pilot Channel).
Explanation: According to TDD handover requirements, an inter-frequency FDD target cell is considered "known" by the UE if it has been measured by the UE during the last 5 seconds. This knowledge impacts the interruption time calculation, specifically through the values of KC (Known Cell) and UC (Unknown Cell) in the Tinterrupt formula.