When the protocol of the communication system is unknown

the analysis of space-time block code parameter is a key research issue for blind receive of Multiple Input Multiple Output signals.Under the circumstance

the model of space-time block code and the receiving signal model are discussed.The relationship between the rank of covariance matrix of receiving signals and the code parameter is revealed.Making use of the distribution of maximum eigenvalue of noise subspace in random matrix theory

the rank of covariance matrix could be exactly estimated

and then the code parameter could be obtained.Simulation results show that the proposed algorithm could not only estimate the space-time block code parameter

but also recognize the first symbol of the code under the condition of unknown code set.