Question: In a TDD (Time Division Duplex) system, what triggers the Base Station (BS) to adjust its code domain power for a power-controlled CCTrCH (Coded Composite Transport Channel) in Downlink using Inner Loop Power Control?
Option 1: SIR (Signal-to-Interference Ratio) measurements at the BS receiver
Option 2: Periodic scheduling of downlink transmissions
Option 3: Receipt of valid power control bits from the UE on the Uplink Traffic Channel
Option 4: Automatic adjustment based on predefined network settings
Explanation: Inner Loop Power Control in the Downlink is dynamically adjusted based on feedback from the User Equipment (UE). The BS adjusts its code domain power for a CCTrCH in response to each valid TPC command, represented by power control bits received from the UE on the Uplink Traffic Channel. These commands are generated based on SIR measurements at the UE receiver, indicating the need for adjustment to maintain optimal signal quality.