Patent ID: 8442135

Claim:
A process for estimating a carrier frequency offset (CFO) θ in a receiver of an Orthogonal Frequency Division Multiplex (OFDM) communication system, said process comprising: receiving a sequence y=(y 0 , y 1 , y 2 . . . , y N−1 ) T corresponding to a pilot sequence x=(x 0 , x 1 , x 2 . . . , x N−1 ) T transmitted by a base station, where N in an integer corresponding to a size of the sequence and T indicates a transposing operator; determining a value of θ which maximizes a function defined as: C ⁡ ( θ ) = - d θ H ⁢ Y H ⁢ X ⁡ ( X H ⁢ X + σ 2 ⁢ Q - 1 ) - 1 ⁢ 1 σ 2 ⁢ X H ⁢ Yd θ where X is a matrix built using the pilot sequence as: X = ( x 0 x N - 1 … x N - L - 1 x 1 x 0 … x N - L - 2 ⋮ ⋮ ⋮ ⋮ x L - 2 x L - 3 … x N - 1 x L - 1 x L - 2 … x 0 ⋮ ⋮ ⋮ ⋮ x N - 1 x N - 2 … x N - L ) L being a presumed length of a channel used to transmit the pilot signal, d θ is a function defined as: d θ = ( 1 , ⅇ 2 ⁢ ⁢ π ⁢ ⁢ i ⁢ ⁢ θ N , … ⁢ , ⅇ 2 ⁢ ⁢ π ⁢ ⁢ ( N - 1 ) ⁢ i ⁢ ⁢ θ N ) T , i being a complex number such that i 2 =−1; Y is a diagonal matrix having y on a main diagonal thereof; σ 2 is a variance of noise and Q is a time covariance matrix of the channel.