Blind recognition of space time block code in MIMO systems

Space time block code (STBC) and vertical Bell layered space-time (VBLAST) signals are widely applied in multiple-input multiple-output (MIMO) systems, and one essential step in the signal interception process is to recognize STBC/VBLAST. As the STBC signal is correlated in time, it has a specific cyclic frequency in higher-order cyclic accumulation, while the VBLAST signal emitted from different antenna is uncorrelated. According to this property, this paper proposes a blind recognition approach for STBC/VBLAST signals based on fourth-order cyclic accumulation (FCC). The recognition process is divided into two steps. In the first step, we first establish the correlation choosing criteria that makes sure all correlations of STBC can generate a statistically cyclic sequence. The cyclic statistic then is estimated by combining the FCC with channel information that provides the peaks phase of the statistically cyclic sequence. The second step compares the estimated cyclic statistic with a detection threshold, which is obtained by given a probability of false alarms. The proposed approach avoids the need for any prior knowledge of the transmitted signal, and can work well in the lowly SNR by employing the advantages of FCC.