Patent ID: 7388935

Claim:
A method of computing, in a baseband radio receiver, a least-squares (LS) channel estimate, ĉ, over a sequence of known transmitted symbols { s ⁡ [ n ] } k - 0 N - 1 given by the equation: ĉ =( S H S ) −1 S H r where S H S is a Fisher information matrix, r is a vector of received samples, and S is a truncated convolution matrix of the transmitted symbols given by: S ≡ [ s ⁡ [ L - 1 ] s ⁡ [ L - 2 ] … s ⁡ [ 0 ] s ⁡ [ L ] s ⁡ [ L - 1 ] … s ⁡ [ 1 ] ⋮ ⋮ … ⋮ s ⁡ [ N - 1 ] s ⁡ [ N - 2 ] … s ⁡ [ N - L ] ] , wherein the information matrix S H S is a nearly Toeplitz matrix based on whitened symbols that are unknown a priori and therefore must be computed in real time, said method comprising the steps of: determining a perturbation matrix (E) in the form of E=ε H ε, for a certain matrix, ε, which stems from truncated portions of the convolution matrix (S) such that the sum of the nearly Toeplitz information matrix (S H S) and the perturbation matrix (E) is a Toeplitz matrix (T); solving for the inversion (X) of the nearly Toeplitz matrix (S H S) by solving the equation: X=T −1 ( B+EX ), where B is a vector or matrix of dimension n by m, said solving step including the steps of: selecting an initial estimate X (0) ; iteratively computing estimates of the inversion X through the recursion: X (n+1) =T −1 ( B+EX (n) ); and computing said least-squares channel estimate, ĉ, to equalize the received signal using X.