Question: For a UTRA FDD UE supporting MIMO with single-stream restriction, what is the primary condition for declaring the probability of event Em (P(Em)) related to HS-SCCH detection performance?
Option 1: The UE successfully decodes data on both HS-SCCH-1 and HS-SCCH-2.
Option 2: The UE is signalled on HS-SCCH-1 but observes DTX in the corresponding HS-DPCCH/NACK field.
Option 3: The UE detects multiple streams simultaneously on HS-SCCH.
Option 4: The UE fails to decode any data on HS-SCCH-1.
Explanation: The correct answer describes the condition for declaring event Em: the UE must be signalled on HS-SCCH-1 but then observes a Discontinuous Transmission (DTX) in the corresponding High-Speed Dedicated Physical Control Channel (HS-DPCCH)/Negative Acknowledgement (NACK) field, assessing HS-SCCH detection performance for single-stream MIMO UEs. Other options are incorrect due to involving successful decoding on multiple channels, simultaneous multi-stream detection (contradicting the single-stream restriction), or a failure to decode data without matching the DTX observation criterion.