Receiver and method in a receiver, for estimating a normalised frequency offset between a transmitter and the receiver in a wireless communication system, based on Orthogonal Frequency Division Multiplexing, OFDM. The method comprises receiving a first pilot signal (yr1) and a second pilot signal (yr2) from the transmitter; computing a Karhunen-Loeve approximation λK(φ), up to any finite order K of a log-likelihood function λ(φ), based on the received pilot signals (yr1, yr2); and estimating the frequency offset by calculating a maximum value of the computed Karhunen-Loeve approximation λK(φ).