In a radio access network of a cellular telecommunications system, a radio network controller (26₁) sets a nominal power level for use by a base station (28_1-1) in transmitting a common transport channel (used for transporting data) over the air interface (32) in a cell for a connection involving a user equipment unit (30). The nominal power level is set by the radio network controller independently of whether the base station supports a differentiated power control scheme (i.e., a power control scheme which allows the base station selectively to adjust the nominal power level, e.g., in accordance with information received from the user equipment unit). In the illustrated embodiments, the differentiated power control scheme allows the base station selectively to adjust the nominal power level in accordance with whether the cell served by the base station is a primary cell or a non-primary cell for the connection with the user equipment unit. When the cell is a primary cell, the base station adjusts the nominal power level by subtracting an offset value from the nominal power level to determine the power level used for actual transmission of data for the common transport channel over the air interface. In differing embodiments, the offset value is acquired either from the radio network controller or is configured locally at the base station. In one mode of the invention, the radio network controller sets the nominal power level using a user plane frame protocol between the base station and the radio network controller. In an example implementation, the common transport channel is a DSCH channel in a UTRAN network.