Patent ID: 7697617

Claim:
A method of synchronising an Orthogonal Frequency Division Multiplexed (OFDM) signal in a communications network, the OFDM signal comprising a plurality of OFDM signal portions with each of the OFDM signal portions comprising a plurality of mutually orthogonal modulated carriers which have been modulated with a respective one of a plurality of known, predetermined symbols, the method comprising the steps of: for each of the OFDM signal portions: a) receiving a respective OFDM signal portion in a receiver, the respective OFDM signal portion having been sent across a channel, b) determining a received phase of each of the plurality of mutually orthogonal modulated carriers of the received OFDM signal portion, c) subtracting a predetermined, transmitted phase of each of the plurality of mutually orthogonal modulated carriers from a respective received phase to provide a phase error for each of the plurality of mutually orthogonal modulated carriers of the received OFDM signal portion, d) determining a plurality of phase error differences of the received OFDM signal portion, each phase error difference being a difference between phase errors of a different pair of adjacent modulated carriers, e) summing the plurality of phase error differences to produce a phase error difference value for the received OFDM signal portion, f) adding a predetermined phase offset value to each of the received phases determined at step b), g) carrying out steps c) to f) in respect of each of the plurality of modulated carriers of the received OFDM signal portion with the phase offset value added, and h) determining a synchronisation position for the received OFDM signal portion based on a minimum of the produced phase error difference values for the received OFDM signal portion; and identifying a boundary between two of the known, predetermined symbols based on the determined synchronisation positions associated with the received plurality of OFDM signal portions and a phase difference between adjacent known, predetermined symbols.