Question: For a UE (User Equipment) with HSDPA capability categories 15-20, what condition triggers the declaration of event Em related to HS-SCCH detection performance?
Option 1: Reception of data on HS-SCCH-2 without corresponding acknowledgement on HS-DPCCH
Option 2: Successful decoding of a transport block on HS-DSCH with no errors
Option 3: Signalling on HS-SCCH-1 accompanied by DTX observed in the corresponding HS-DPCCH/NACK field
Option 4: Activation of MIMO operation for downlink control channels
Explanation: The correct answer directly relates to the condition specified for declaring event Em, crucial for assessing HS-SCCH detection performance. This scenario involves UE being signalled on HS-SCCH-1 but observing DTX in the corresponding HS-DPCCH/NACK field, highlighting a mismatch affecting detection reliability, vital for evaluating control channel signalling efficiency in HSDPA-enabled UEs.