Automatic Identification of Space-Frequency Block Coding for OFDM Systems

Signal identification has emerged as an enabling technology for intelligent wireless communication systems with applications in military and commercial fields. One of recent trends in this research topic is to propose identification algorithms for multiple antenna (MA) systems with multi-carrier (MC) transmissions. The previously reported investigations are limited to space-time block code (STBC) systems with MC transmissions. However, practical systems include also space-frequency block code (SFBC) schemes with MC transmissions. In this paper, we develop and analyze an SFBC identification algorithm for MA orthogonal frequency-division multiplexing (OFDM) transmission for the first time in the literature. Analytical expressions for the time-domain properties of the Alamouti and spatial multiplexing SFBC-OFDM signals are derived as the basis of the identification process. The proposed algorithm is divided into two steps. The first step estimates the cross-correlation function of pairs of signals received from different antennas, while the second step employs a false-alarm based test for decision making. The proposed algorithm avoids the need for a priori knowledge of the modulation format, channel coefficients, signal-to-noise ratio (SNR) value, and the starting time of OFDM symbols. Simulation results show the ability of the proposed algorithm to provide an acceptable identification performance in the presence of transmission impairments, even at relatively low SNR values. These favorable results are achieved with acceptable computational cost.