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In this paper, in order to detect the number of transmitting antenna in MIMO communication systems, it is proposed that the techniques such as AIC & MDL, which have been primarily designed so as to detect the number of Gaussian sources, are applied. Then a hypothesis testing based method for recognizing the type of modulation in MIMO communication systems with block orthogonal codes is suggested; in which in order to reduce the complexity of the traditional methods, simpler likelihood functions for testing hypotheses are applied. Furthermore, because in all modulation scheme detection methods, a proper estimation of channel gain (channel matrix) is required; in this paper, a new and efficient method based on SAGE iterative algorithm for estimation of channel matrix in MIMO communication system with space-time block codes is proposed. At the end of this paper, the performance and effectiveness of all proposed modules are separately and jointly analyzed by numerical simulations.