Patent ID: 7218693

Claim:
A method for estimating a channel in a packet based transmission system having a predetermined number of tones (N), wherein the channel has a channel order (L), where L>1, and having a predetermined and stored long sequence (X), comprising the steps of: pre-computing at least one channel estimation matrix (R −1 ) which equals (F H {tilde over (D)} H {tilde over (D)}F) −1 having dimension of width and length equal to the channel order (L), where matrix F is a Fourier transform matrix, matrix {tilde over (D)} is a matrix having the long sequence X as its diagonal while all other elements equal zero, where an Hermitian operator H is a conjuciate transpose, matrix {tilde over (D)} H is the Hermitian of matrix {tilde over (D)}, F H is the Hermitian of Discrete Fourier Transform (DFT) matrix F; storing (L+1) 2 /4 elements of the channel estimation matrix R −1 in a storage means; detecting a continuous time signal from a transmitting device; converting the continuous time signal into a digital signal; transforming the digital signal into a frequency domain vector (V) of the digital signal using a discrete Fourier transform filtering means; multiply the matrix {tilde over (D)} by the frequency domain vector (V) to provide a vector (S); calculating the inverse discrete Fourier transform of the vector (S); selecting from the inverse discrete Fourier transform of vector (S) a grouping of elements equal to the first predetermined length (L) to provide a complex vector having length equal to the first predetermined length (1); regenerating one of the at least one channel estimation matrix (R−I) having dimension of width and length equal to the channel order (L) from the (L+1) 2 /4 stored elements; multiplying the precomputed channel estimation matrix (R −1 ) by the complex vector to produce a first product; and calculating the discrete Fourier transform of the first product to produce an estimation of the channel.