ABSTRACTinvokes L array elements or sensors. At the transmitter side Alamouti's STBC scheme based on two transmit antennas is A multiple-input multiple-output (MIMO) space-division employed for encoding the transmitted symbols, in order to multiple-access (SDMA) system is presented and investigated, achieve a double-order transmit diversity. By contrast, at the when the space-time block coded (STBC) In this contribution we focus on the reduced-rank MMSE Specifically, three classes of reduced-rank MMSE techniques detection of the STBC assisted SDMA signals. Specifically, are investigated in conjunction with the proposed SDMA sys-three classes of reduced-rank MMSE techniques are extended tem. The three classes of reduced-rank MMSE algorithms are and investigated in conjunction with the proposed SDMA sysderived, respectively, based on the principles ofprincipal com-tem, so as to achieve low-complexity MMSE detection. The ponents (PC), cross-spectral metric (CSM) and Taylor poly-three classes of reduced-rank MMSE algorithms are derived, nomial approximation (TPA). Our study and simulation re-respectively, based on the principles of PC [4] - [7], CSM [6,8] sults show that the reduced-rank MMSE detection is capable and TPA [9]. The characteristics of these reduced-rank MMSE of achieving a satisfactory trade-off between the affordable de-algorithms are considered, and their BER performance is intection complexity and the achievable detection BER perfor-vestigated by simulation, when communicating over indepenmance. dent Rayleigh fading channels. Our study and simulation results show that the reduced-rank MMSE detection is capable