Patent ID: 8503556

Claim:
A 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, wherein the method comprises the following steps: obtaining by a receiver device at least one initial channel estimate Ĥ (0) over at least one OFDM symbol of said signal; calculating by said receiver device at least one soft information, from said at least one initial channel estimate Ĥ (0) , delivering a N×N soft information matrix, N being the number of subcarriers of said at least one symbol; and updating said at least one initial channel estimate Ĥ (0) by 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 Ĥ 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, Σ 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 Σ, wherein one singular value of said matrix Σ 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 , Σ s and V s which contain the S remaining columns of matrices U, Σ and V respectively; and calculating channel estimates by applying said matrices U s , Σ s and V s in an expectation maximization algorithm.