Question: In a TDD/TDD intra-frequency or inter-frequency handover scenario, as per 3GPP specifications, what determines whether a target cell is considered "known" to the User Equipment (UE), influencing the interruption time calculation?
Option 1: The strength of the signal received from the target cell.
Option 2: Whether the UE has previously received a RRC message indicating the target cell as known.
Option 3: If the target cell's SFN (System Frame Number) decoding is required upon handover.
Option 4: If the target cell was measured or had a connected radio link within the last 5 seconds.
Explanation: According to the specifications, a TDD/TDD intra-frequency or inter-frequency target cell is considered "known" by the UE if either of two conditions are met: (1) the target cell was measured during the last 5 seconds, or (2) the UE had a radio link connected to the target cell during the last 5 seconds. This knowledge affects the interruption time calculation, specifically through the values assigned to KC (Known Cell) and UC (Unknown Cell) variables in the Tinterrupt formula.