Multiple antenna systems improve the spectral efficiency without increasing power or bandwidth, theoretically, the capacity increases with the number of antennas deployed. MIMO technique also gained a considerable amount of interest as technique to increase the data rate through spatial multiplexing or enhance the quality of transmission through the exploitation of diversity [1]. In multiuser MIMO downlink communications [2], a base station communicates with several co-channel users in the same frequency and time slots. Therefore it is necessary to design a transmitter that able to suppress co-channel interference (CCI) because co-channel interference consider as major limitation factor for the system capacity. The focus of this paper is on spatial diversity techniques in a downlink wireless communication system, where a base station (BS) could simultaneously serve multiple users, which required to deployed beamforming [3-4] at BS to suppress CCI to end users and maximize overall capacity. Many techniques have been adopted to suppress the CCI. For example in [5], the pre-processing of the signal at the BS was employed to completely cancel the CCI at the receiver for each user, while in [6] the block-diagonalization was proposed. Both [5] and [6] restricted to use transmitting antennas to be greater