Patent ID: 7310378

Claim:
A method of estimating a transmission channel on the basis of a signal received after transmission through said transmission channel, said signal being a multicarrier signal constructed on a time/frequency lattice defined by a frequency axis and a time axis, and comprising frames having M×N symbols distributed over M subcarriers each of which is divided into N determined symbol times, each frame comprising P pilot symbols distributed timewise and frequencywise in such a way as to cover the frame according to a lattice structure, where the numbers M, N and P are nonzero integers, the pilot symbols comprising on the one hand symbols known as real pilot symbols, transmitted as symbols having a real value, and on the other hand symbols known as pure imaginary pilot symbols, transmitted as symbols having a pure imaginary value, the method comprising the steps of: a) selecting one or more values z k of the signal received corresponding to one or more real pilot symbols of respective values c k on the one hand, and one or more values z l of the signal received corresponding respectively to one or more pure imaginary pilot symbols of respective values c l on the other hand, these pilot symbols being sufficiently close together both along the frequency axis and along the time axis for it to be possible to consider that the fading of the signal through the transmission channel has had a substantially identical (in modulus and in phase) complex value α for these pilot symbols; b) determining complex numbers u and v and a real number λ by minimizing the following least squares expression: ɛ 1 2 = ∑ k ⁢  Re ⁡ ( z k · u ) - λ · c k  2 + ∑ 1 ⁢  Re ⁡ ( z 1 · v ) - λ · c 1  2 where the sign Σ denotes the summation operator, where ∥x∥ denotes the absolute value operator for the real variable x or the modulus of the complex variable x, where λ is a real number, where k is an integer index between 1 and the number of values z k , where u and v are orthogonal (that is to say Re(u*.v)=0, where Re(w) denotes the real part operator for the complex number w, and where w* denotes the complex conjugate of the complex number w), such that ∥u∥=∥v∥, c) determining an estimated value {circumflex over (α)} of the value α of the fading of the signal through the transmission channel for the pilot symbols concerned, by calculating: {circumflex over (α)}=λ/u.