Method and arrangement for supporting transmission over a Digital Subscriber Line (xDSL) in the presence of Repetitive Electrical Impulse Noise (REIN). The method involves obtaining a power spectrumof the measured Quiet Line Noise (QLN) for the xDSL,where it is assumed that the QLN comprises a REIN contribution. Aperiodicityis detectedin the QLN power spectrum,and the repetition interval of the periodicityis determined.The power spectrumof the REIN is then estimated, based on the repetition interval of said periodicity. Thus, information associated with the estimated REIN power spectrummay be provided for use by a communication unit, such that mitigation of potentially unfavorable influence/effects of the REIN on said transmission over the xDSL.