A base station transmits blocks, in successive transmission time intervals, to radio terminals, over communication channels shared between the radio terminals comprising traffic channels and control channels associated with traffic channels, some of the transmitted blocks being positively or negatively acknowledged by the radio terminals. With regard to a radio terminal: a quality indication relative to said traffic channel is determined; a quantity relative to acknowledgements transmitted to the base station beforehand is determined; a transmission power on the traffic channel and/or the associated control channel is calculated, for the next corresponding transmission time interval, from said quality indication and said quantity relative to acknowledgements.