Patent ID: 8842755

Claim:
A process for decoding a signal being representative of a Space Time Block coding (STBC) or Space Frequency Block coding (SFBC) based on a transmission, firstly, of a pair of finite-alphabet complex symbols x 1 and x 2 , and secondly, of symbols −x 2 * and x 1 *, wherein * is a conjugate operation, during two parallel channels (SFBC), wherein the process comprises: receiving an OFDM signal, from at least one antenna, by a receiver comprising one single antenna; performing an OFDM demodulation in order to generate N frequency domain representations of the received OFDM signal, each N frequency domain representation being associated to one carrier; performing a decoding process applied on the demodulated OFDM signal, in order to group the received OFDM signal in word code, Y=(y 1 , y 2 ), being representative of the received OFDM signal received during two signaling periods (STBC) or two parallel channels (SFBC); decoding the word code, Y=(y 1 , y 2 ), in order to compute transmitted symbols x 1 and x 2 in accordance with a formulation, [ y 1 y 2 * ] = [ h 1 h 2 h ~ 2 * - h ~ 1 * ] ⁡ [ x 1 x 2 ] + [ n 1 n 2 * ] Or y = Hx + n wherein H is a matrix, h 1 and h 2 are representative of the channel applicable to the transmission of x 1 and x 2 while {tilde over (h)} 1 ′ and {tilde over (h)} 2 are representative of the channel applicable to the transmission of −x 2 * and x 1 *, and wherein n 1 and n 2 are noise, wherein decoding the word code comprises: applying a lattice reduction algorithm on the matrix H, H=(b 1 , b 2 ), in order to transform the matrix H into a reduced matrix Hred=(b′ 1 , b′ 2 ) comprising vectors that are substantially orthogonal, wherein the lattice reduction algorithm on each carrier k is based on an iterative algorithm that was initialized based on values (b 1 k-1 , b 2 k-2 ) computed at a preceding iteration; wherein the lattice reduction algorithm comprises: checking the correlation by testing whether I Re {b 1 , b 2 >}1≦½Il b 1 Il 2 and I Im {<b 1 , b 2 >}1≦½Il b 1 Il 2 , and, if not, replacing b 2 with b 2 - ⌊ ( b 1 , b 2 )  b 1  2 ⌉ ⁢ b 1 and repeating the checking step again; and performing a detection process on the reduced matrix Hred in order to minimize noise and interference immunity.