Embodiments relate to a method, and a device for performing the method, for allocating power levels to a transmission in a DSL network, the method including: identifying a first and second geographical region as being associated with a subscriber line in the DSL network; defining a first spectral mask having a first set of power levels over a range of frequencies, wherein the first set of power levels are tailored according to a Radio Frequency, RF, environment of the first geographical region; defining a second spectral mask having a second set of power levels over the range of frequencies, wherein the second set of power levels are tailored according to an RF environment of the second geographical region; and constructing a transmit spectral mask for the subscriber line, the transmit spectral mask based on a combination of the first and second spectral masks, including, for each frequency in the range of frequencies, using the minimum power level for that frequency from the first and second spectral masks.