Question: For FDD UEs supporting MIMO-only with single-stream restriction-STTD disabled-asymmetric CPICHs, what is the primary indicator for assessing HS-SCCH detection performance?
Option 1: Probability of successful HS-DPCCH/NACK field transmission (P(Em)) when signalled on HS-SCCH-1
Option 2: Average power boost of CPICH in asymmetric mode
Option 3: Number of retransmissions requested via HS-DPCCH/NACK
Option 4: UE's reported RSRP during MIMO operation
Explanation: The detection performance of the HS-SCCH for the specified MIMO configuration is directly tied to the probability of event Em (P(Em)), which occurs when a UE is signalled on HS-SCCH-1 but observes DTX in the corresponding HS-DPCCH/NACK field. This scenario specifically tests the UE's ability to correctly detect and respond to HS-SCCH signals under defined conditions, making P(Em) the key performance indicator for this aspect of HS-SCCH detection.