This invention provides a method for dynamically adjusting the transmitter power (PTX) and data rate in a communications system. The scheme is specifically intended for wireless systems based on Code Division Multiple Access (CDMA) or on Multiple Input Multiple Output (MIMO) technology, but can be applied to all systems in which a so-called “Multi-User Detector” can be used. The method includes that the decision whether to increase or decrease the transmitter power (PTX) is based on the Signal to Interference plus Noise Ratio (SINR) at the receiver (S2), whereby the receiver (S2) determines the interference (PIF) with a Multi-User Detector. The interference level (PIF) is then communicated to the sender (S1) or alternatively the receiver (S2) determines the optimal transmitter power level (PTX) and communicates this level to the sender (S1). The proposed method reduces the power consumption and increases the performance e.g. in CDMA based systems.