Method and system for controlling the transmission power of certain parts of a radio transmission

A method for controlling transmission power in a data transmission system comprising a first device and a second device and in between them a two-way data transmission connection that employs Code Division Multiple Access, where the first device transmits to the second device user data on a data channel, and the second device transmits to the first device user data on a data channel and control information on a control channel, and a transmission arranged in a time slot comprises a user data field corresponding to a data channel and at least a first and a second control information field corresponding together to the control channel, said method comprising the steps of:

• determining a first transmission power level, a second transmission power level and a third transmission power level;
• and
• transmitting from the second device to the first device during a time slot by applying said first transmission power level to the transmission of the user data field, said second transmission power level to the transmission of the first control information field and said third transmission power level to the transmission of the second control information field, and also applying a first spreading code to the transmission of the user data field and a second spreading code, different than said first spreading code, to the transmission of at least one of the first control information field and the second control information field.