Question: For a UTRA FDD UE supporting MIMO with single-stream restriction and TX Diversity on DL Control Channels, what is the primary condition for declaring the probability of event Em (P(Em)) related to HS-SCCH detection performance?
Option 1: Reception of data on HS-DSCH while in idle mode.
Option 2: Successful decoding of a message on HS-SCCH-2 indicating handover.
Option 3: Signaling on HS-SCCH-1 with observed DTX in the corresponding HS-DPCCH/NACK field.
Option 4: Failure to detect CPICH within a specified time frame after cell selection.
Explanation: The correct answer, Option 3, directly relates to the condition described for declaring the probability of event Em (P(Em)), which is specifically when the UE is signaled on HS-SCCH-1 but observes Discontinuous Transmission (DTX) in the corresponding High-Speed Dedicated Physical Control Channel (HS-DPCCH)/Negative Acknowledgement (NACK) field. This scenario assesses the detection performance of the High-Speed Shared Control Channel (HS-SCCH) under specific MIMO conditions. The other options do not accurately describe the condition for declaring P(Em) as per the given context, involving incorrect scenarios or elements not directly related to the declaration of event Em.