Channel tracking in an orthogonal frequency-division multiplexing system

In a communications system wherein a receiver receives signals comprising a plurality of symbols, wherein each symbol is represented over a plurality of sub carriers each having distinct frequency extent and wherein an amplitude and relative phase of the subcarriers are selected by a transmitter from a predetermined set of possible values known to the receiver in advance, so as to represent data to be conveyed by the signals, at least some of which selections are not known to the receiver in advance of receiving the signals, and wherein reception of a signal by the receiver is subject to at least phase and/or timing noise and uncertainty as to one or more of phase of the signal and the timing of the symbols, a method for determining at least approximations of the phase and/or timing, comprising:

• receiving a symbol comprising a plurality of components each represented as a signal over a distinct one of a plurality of subcarriers each having distinct frequency extent, the symbol having thereon imposed uncertainty as to one or more of phase and frequency;
• transforming the components into transformed component signals that are substantially independent of the information carried on each of the components;
• and
• using the transformed signals in an estimation of the imposed uncertainty.