Patent ID: 7844004

Claim:
A method of estimating carrier frequency offset introduced on an RF multicarrier signal received via a transmission channel on a direct downconversion analog receiver, comprising: a) generating a preamble comprising multiple sets of training symbols, b) transmitting the preamble via the channel and receiving it on the receiver, c) introducing a predetermined artificial carrier frequency offset on at least one of the sets of training symbols, d) determining a carrier frequency offset estimate from each set of training symbols of the received preamble by an estimation method which has a higher precision for a first range of carrier frequency offset values and a lower precision for a second range of carrier frequency offset values, wherein each of the carrier frequency offset estimates is determined by a direct algebraic relationship between a number of the training symbols of the considered set, the direct algebraic relationship cancelling out IQ imbalance; and e) exploiting the direct algebraic relationship to take noise into account in determining an overall carrier frequency offset estimate from the carrier frequency offset estimates; wherein the predetermined artificial carrier frequency offset is chosen for shifting the carrier frequency offset of that set of training symbols of the generated preamble to the first range of carrier frequency offset values, wherein the carrier frequency offset is modelled as a phase rotation and that the determining of a carrier frequency offset estimate comprises determining a phase rotation for each received set of training symbols by the direct algebraic relationship, wherein the direct algebraic relationship for determining the phase rotation for each received set of training symbols is based at least in part on the following equation: y ⁡ ( k ) + y ⁡ ( k + 2 ⁢ l ) y ⁡ ( k + l ) = 2 ⁢ cos ⁢ ⁢ φ wherein y(k), y(k+l) and y(k+2l) are three equal training symbols of the respective set of the received preamble, spaced by a delay l in time, and wherein φ is the phase rotation between these training symbols.