Abstract: The method is for controlling the transmission power for a session in a system when transmitting data via a telephone line by using a digital subscriber line between a user terminal and a central unit. The transmission power is increased or decreased between given limit values so that the transmission power is kept as low as possible while still providing a sufficient transmission quality. The transmission quality, and therefore the transmission power, is controlled by the value of the signal-to-noise ratio and the number of bit errors BER within a given time interval.

Abstract: The invention is concerned with a method for controlling the transmission power for a session in a system for transmitting data via a telephone line by using a digital subscriber line between a user terminal and a central unit. In the method, the transmission power is increased or decreased between given limit values so that the power is kept as low as possible, while still providing sufficient transmission quality. The quality criteria according to which the transmission power is controlled consistis of the value of the Signal to Noise Ratio (S/N), and the number of bit errors BER within a given time interval.