A method, program and apparatus for transmitting a signal in a time slot of a channel comprising a plurality of time slots. Using a transmitter having a processor and a power amplifier, the method comprises: retrieving a reference ramp pattern from a memory; determining an output power level for the slot from a plurality of possible output power levels, each requiring a respective corresponding ramp pattern; executing software on the processor to apply a scaling function to the reference ramp pattern in dependence on the determined output power level, thus generating a scaled ramp pattern corresponding to the pattern required for that determined level; supplying the scaled ramp pattern to a control input of the power amplifier, to control the gain of the power amplifier during the time slot; and using the power amplifier, controlled according to the scaled ramp pattern, to transmit the signal in the time slot.