I. Introduction
Orthogonal Frequency Division Multiplexing (OFDM) [1] has some great advantages as: Low complexity of implementation, Orthogonality of subcarriers in transmission, and at the receiver side easy equalization. MIMO-OFDM demonstrates benefits of both MIMO and OFDM like enhancement in channel capacity [2] and combat inter symbol interference (lSI) as compare to single input single output (SISO)-OFDM. Because of all these features MIMO-OFDM systems have recently attracted great interest. In MIMO-OFDM, detection plays very critical role at the receiver. Several detection techniques are available in the literature, optimal as well as suboptimal. For coherent detection all conventional detectors require channel state information (CSI). In wireless communication generally training symbols are used to find CSI. However, transmission of training symbols reduces spectral efficiency in wireless communication systems, because this field of communication has very scarce bandwidth resource. Secondly in high mobility MIMO-OFDM system the transmission of the CSI is not often effective. Furthermore, CSI may cause a wrong detection if it is attenuated during transmission [3]. Blind multiuser detection [4] is an innovative and efficient method in which retransmission of CSI is not used in MIMO OFDM system.