Channel estimating method in an orthogonal frequency division multiplexing, OFDM, system transmitting a signal over a channel, said signal comprising a plurality of symbols, wherein each of said symbols comprises at least one null subcarrier, said method comprising the following steps: - obtaining at least one initial channel estimate Ĥ over at least one OFDM symbol of said signal; - calculating at least one soft information, from said at least one initial channel estimate Ĥ, delivering a N × N soft information matrix, N being the number of subcarriers of said at least one symbol; said method being characterized by: - updating said at least one initial channel estimate Ĥ bv performing a truncated singular value decomposition of a partial FFT matrix Ω L DP, wherein said partial FFT matrix comprises only the first L DP columns and the rows N DP of an FFT matrix of said N × N soft information matrix, said N DP rows corresponding to modulated subcarriers of said received signal, including data and pilot symbols and excluding said at least one null subcarrier, delivering an improved channel estimate H ^ TSVD − EM i, said updating step comprising: - decomposing said partial FFT Matrix Ω L DP as Ω L DP = UΣV H, where the matrix U is an N DP × N DP unitary matrix, E is an N DP × L DP diagonal matrix with non negative real numbers on the diagonal, and V is an L DP × L DP unitary matrix; - applying a threshold value T for at least one singular value of said matrix E, wherein one singular value of said matrix E is kept unchanged when greater than said threshold T and is set to null when lower than said threshold T; - deriving resulting truncated matrices U S, ∑ S and V S which contain the S remaining columns of matrices U, E and V respectively; - calculating channel estimates by applying said matrices U S, ∑ S and V S in an expectation maximization algorithm. - obtaining at least one initial channel estimate Ĥ over at least one OFDM symbol of said signal; - calculating at least one soft information, from said at least one initial channel estimate Ĥ, delivering a N × N soft information matrix, N being the number of subcarriers of said at least one symbol; said method being characterized by: - updating said at least one initial channel estimate Ĥ bv performing a truncated singular value decomposition of a partial FFT matrix Ω L DP, wherein said partial FFT matrix comprises only the first L DP columns and the rows N DP of an FFT matrix of said N × N soft information matrix, said N DP rows corresponding to modulated subcarriers of said received signal, including data and pilot symbols and excluding said at least one null subcarrier, delivering an improved channel estimate H ^ TSVD − EM i, said updating step comprising: - decomposing said partial FFT Matrix Ω L DP as Ω L DP = UΣV H, where the matrix U is an N DP × N DP unitary matrix, E is an N DP × L DP diagonal matrix with non negative real numbers on the diagonal, and V is an L DP × L DP unitary matrix; - applying a threshold value T for at least one singular value of said matrix E, wherein one singular value of said matrix E is kept unchanged when greater than said threshold T and is set to null when lower than said threshold T; - deriving resulting truncated matrices U S, ∑ S and V S which contain the S remaining columns of matrices U, E and V respectively; - calculating channel estimates by applying said matrices U S, ∑ S and V S in an expectation maximization algorithm. - updating said at least one initial channel estimate Ĥ bv performing a truncated singular value decomposition of a partial FFT matrix Ω L DP, wherein said partial FFT matrix comprises only the first L DP columns and the rows N DP of an FFT matrix of said N × N soft information matrix, said N DP rows corresponding to modulated subcarriers of said received signal, including data and pilot symbols and excluding said at least one null subcarrier, delivering an improved channel estimate H ^ TSVD − EM i, said updating step comprising: - decomposing said partial FFT Matrix Ω L DP as Ω L DP = UΣV H, where the matrix U is an N DP × N DP unitary matrix, E is an N DP × L DP diagonal matrix with non negative real numbers on the diagonal, and V is an L DP × L DP unitary matrix; - applying a threshold value T for at least one singular value of said matrix E, wherein one singular value of said matrix E is kept unchanged when greater than said threshold T and is set to null when lower than said threshold T; - deriving resulting truncated matrices U S, ∑ S and V S which contain the S remaining columns of matrices U, E and V respectively; - calculating channel estimates by applying said matrices U S, ∑ S and V S in an expectation maximization algorithm.