To improve the bit rate, the effectiveness of wireless trans- mission systems and limit the effects of fading transmission channel, an increased attention have recently been paid to MIMO systems. In fact, Alamouti’s space-time block code is introduced in various wireless stan- dards and systems. This manuscript deals with the problem of presence identification as well as blind separation of Orthogonal Space-Time Block Code (OSTBC) in the context of non data aided. KEY WORD: MIMO channel, OSTBC, ICA, Alamouti’s code, BSS of underdetermined mixture.