a method and devices are disclosed for conveying information related to fast power control between a mobile sation and a radio access network in a cellular radio system . frames of payload information are transmitted during certain first period of an active circuit - switched communication connection , said first period corresponding to a period where payload information exists for transmission . information related to fast power control is inserted into the frames of payload information transmitted during said first period of an active circuit - switched communication connection . the transmission of frames of payload information is temporarily discontinued for the duration of a certain second period of an active circuit - switched communication connection , said second period corresponding to a period where payload information temporarily does not exist for transmission . updating messages are transmitted according to a certain timetable during said second period . information related to fast power control is insrted into the updating messages transmitted during said second period of an active circuit - switched communication connection .