An apparatus, method and program for processing a signal received over a wireless channel. The apparatus comprises: a channel searcher configured to determine a profile of the channel in the form of energy values for a plurality of rays at respective channel positions, and an equalizer for equalizing the signal based on a variable window of the equalizer. The channel searcher is configured to estimate dispersion of the channel by determining a measure of variance of ray distance from a reference position within the channel profile weighted by ray energy. The equalizer is coupled to the channel searcher and arranged to adapt the window in dependence on the measure of energy-weighted ray distance variance.