In this paper, a novel radio modem architecture for a wireless local area network is proposed. The main focus is to reduce the power consumption, which is a crucial requirement for portable devices. In particular, the paper describes a new control architecture which is in charge of properly adapting the transmission power to the link?s condition by controlling the transmission bit rate and the capacity request scheme. By using fuzzy logic and internal model control, the scheme manages to adapt the bit rate, granting at the same time the reduction of the power consumption and the satisfaction of the Quality of Service requirements.