A process for decoding a signal being representative of a Space Time or Frequency Block coding during two signaling periods (STBC) or two parallel channels (SFBC) is provided. The process receives an OFDM signal received from at least one antenna. The process also performs an OFDM demodulation in order to generate N frequency domain representations of the received signal. Then the process performs a decoding process on said OFDM demodulated signal and groups the received signal in word code, Y=(y1, y2), to represent the signal that was received during two signaling periods (STBC) or two parallel channels (SFBC). The word code is then decoded into a matrix after which a lattice reduction algorithm is applied to the matrix in order to transform the matrix into a reduced matrix having a near orthogonal vector. Then it performs a detection process on the reduced matrix to improve noise and interference immunity.