Question: In E-UTRA, during SCell activation, if a UE's PCell is interrupted, what is the latest subframe by which the UE must send its first non-zero CQI index CSI report for SCell1, considering no uplink resource constraints?
Option 1: Subframe (m+8) for both FDD and TDD PCells
Option 2: Subframe (m+39) for FDD PCell and (m+40) for TDD PCell
Option 3: The next available uplink resource after subframe (m+39) for both FDD and TDD PCells, if (m+39) has no resources
Option 4: Subframe (m+39) for both FDD and TDD PCells, with flexibility to use the next available uplink resource if (m+39) lacks resources
Explanation: During SCell activation, a UE must start sending CSI reports for SCell1 with a non-zero CQI index at the latest in subframe (m+39) for both FDD and TDD PCells. If subframe (m+39) has no uplink resources for a valid CSI report, the UE uses the next available uplink resource.