Method and arrangement in a network entity for supporting link adaptation in a wireless communication system. The method comprises obtaining 204 one or more predicted parameters related to the quality of a radio link. The method further comprises measuring 206 one or more actual parameters, corresponding to the one or more predicted parameters. The method further comprises deriving 208 one or more error distributions based on the difference between the predicted and actual one or more parameters, from which error distributions a link adaptation margin estimate is derived, based on a predetermined radio link quality target. The link adaptation margin estimate is then used for supporting link adaptation for the radio link.