BLIND RECOGNITION OF ORTHOGONAL SPACE-TIME BLOCK CODES BASED ON THE KURTOSIS OF CROSS-CORRELATIONS LAGS

Abstract : In the communication interception framework (COMINT, i.e. COMmunication INTelligence), a quality coding scheme recognition is the first step that needs to be addressed in order to extract the information from intercepted signals. In this paper, we present a new blind recognition algorithm of Orthogonal Space-Time Block Codes (OSTBCs) based on a cross-correlation analysis over linear combinations of the transmitted signals. The latter analysis exploits the temporal redundancy and the structure of the OSTBCs. To classify the intercepted signals, different classification methods relying on the Kurtosis of cross-correlations have been considered. Experimental results show that our method performs well in a variety of conditions such as rough estimate of the signal bandwidth and the carrier frequency, presence of noise, channel unknown to the receiver and non-synchronism between the transmitter and the receiver. The study is carried out using the Alamouti code, but good results have been obtained using the proposed method in order to identify an OSTBC with 3 antennas in the transmitter.