Space-Frequency Transmit Diversity in Multi-user Multiple Antenna Systems

In this work, we investigate Multi-User Multiple-Input Multiple-Output (MU-MIMO) systems within the frame of an Orthogonal Frequency Division Multiple Access (OFDMA) communication scheme. We look at the case where two User Terminals (UT) having two transmit antennas each, are simultaneously communicating in Up-Link (UL) with the Base Station (BS) equipped with two receive antennas. We propose the use of transmit precoding at the UT and linear decoding augmented with successive cancellation at the BS and show that this combination can support simultaneous parallel transmissions while preserving almost intact the quality of the individual user´s links even though they use the same time and frequency resources.