Question: In E-UTRA, what is the defined bit payload per sub-frame for CQI information transmitted using PUCCH format 2?
Option 1: 2 bits, with optional extension to 4 bits under specific transmission conditions
Option 2: 8 bits, divided into two 4-bit segments for redundancy
Option 3: 4 bits, applicable to all transmissions without exclusion due to DTX
Option 4: Variable, dependent on the number of antenna ports utilized (e.g., 2 bits per port)
Explanation: According to E-UTRA specifications for PUCCH format 2, the CQI information bit payload is consistently defined as 4 bits per sub-frame. This fixed payload ensures standardized transmission and decoding processes, irrespective of other transmission parameters like antenna ports or DTX (Discontinuous Transmission) states. This consistency aids in maintaining predictable performance metrics, such as the CQI block error probability (BLER).