The invention relates to correcting codes for encoding and decoding a data signal. A signal including data variables is coded into a signal including the data variables and parity variables. The encoding and decoding operations are based on a parity check matrix comprised of a systematic matrix and a parity matrix and having rows corresponding coefficients of parity equations and distributed into decoding windows of same size. In order to increase convergence of the iterative decoding, the elements of at least one column of the systematic matrix associated with a decoding window are “0s”, except for a single element which is a “1”. A data variable is only involved in one equation of the window and not involved in solving the equations of other windows as long as the solving of equations of the window is not achieved.