Question: In a 1.28 Mcps TDD handover scenario, what determines whether the interruption time (Tinterrupt) calculation includes the term "50*KC" with KC equal to 1?
Option 1: The target cell is an inter-frequency FDD cell that the UE has measured within the last 5 seconds.
Option 2: The handover is from TDD to FDD and the UE has prior knowledge of the target cell's frame structure.
Option 3: The RRC message indicates a known target cell for the 1.28 Mcps TDD/FDD handover, regardless of measurement history.
Option 4: The UE's current serving cell is a known FDD cell, influencing the handover to any TDD target cell.
Explanation: According to the specifications, KC equals 1 if a **known** target cell is indicated in the RRC message for a 1.28 Mcps TDD/FDD handover, directly impacting the interruption time calculation by including the "50*KC" term. This highlights the importance of RRC messaging in handover procedures for efficiently managing radio resources during the transition between cells or technologies.