Question: What is implied by the "DTX to ACK probability for NPUSCH format 2" in an NB-IoT Base Station context?
Option 1: The likelihood of successfully transmitting ACK on a wanted signal with full power.
Option 2: The chance of receiving an ACK when a UE is out of the cell's coverage area.
Option 3: The probability of falsely detecting an ACK in a noise-only scenario for NPUSCH format 2 transmissions.
Option 4: The rate at which an NB-IoT Base Station switches between supported sub-carrier spacings.
Explanation: This question tests understanding of the specified performance metric (DTX to ACK probability) in the context of NB-IoT Base Stations. Option 3 is correct because "DTX" stands for Discontinuous Transmission, implying no signal is sent (only noise is present), and the question specifically mentions the detection of an ACK in such a scenario for NPUSCH format 2 transmissions. This scenario directly relates to measuring false positives in ACK detection under noise conditions, which is crucial for understanding radio transmission reliability in telecom networks.