In a receiver for processing OFDM encoded signals, wherein the OFDM encoded digital signals are transmitted by means of a symbol in each of subcarrier frequency channels, with at least some of said subcarriers containing user data symbols, an initial estimate of a channel frequency response is formed from magnitudes of user data symbols received in those subcarriers. Then, a correlation function of a channel impulse response is estimated by performing an inverse Fourier transform on the initial estimate of the channel frequency response, and the length of the channel impulse response is estimated by examining peaks in the estimated correlation function of the channel impulse response.