A channel estimating method is provided for a signal transmitted in an orthogonal frequency division multiplexing (OFDM) system, wherein an OFDM symbol of the signal has at least one null subcarrier set in its defined bandwidth. The method includes: obtaining at least one initial channel estimate over at least one OFDM symbol of a received signal; processing the at least one initial channel estimate for delivering at least one soft information in a form of a complete matrix; and updating the at least one initial channel estimate by performing a truncated singular value decomposition of a partial FFT matrix. The partial FFT matrix includes only the first LDP columns and the rows NDP of an FFT matrix of the complete matrix, the NDP rows corresponding to modulated subcarriers of received signal, including data and pilot symbols and excluding the at least one null subcarrier, delivering an improved channel estimate.