Question: In a TDD (Time Division Duplex) network, when a UE (User Equipment) is in Cell-FACH (Forward Access Channel) state and the parameter `Treselection` is set to 0, which of the following metrics is used for cell re-selection to another TDD cell?
Option 1: CPICH Ec/Io (Common Pilot Channel Ec/Io)
Option 2: GSM Carrier RSSI (Received Signal Strength Indicator)
Option 3: P-CCPCH RSCP (Primary Common Control Physical Channel Received Signal Code Power)
Option 4: UE Transmit Power
Explanation: According to the specified requirements for radio resource management in TDD mode, when a UE is in Cell-FACH state and `Treselection` is set to 0, P-CCPCH RSCP is the metric used for cell re-selection evaluations to another TDD cell. This ensures that the handover decision is based on the signal strength of the primary control channel, which is crucial for maintaining reliable communication in a TDD network.