Investigation of multiuser detection schemes for Multiple Transmit/Multiple Receive antenna aided OFDM-SDMA systems

Multiple Transmit-Multiple Receive (MTMR) Orthogonal Frequency-Division Multiplexing /Space-Division Multiple Access (OFDM-SDMA) systems have recently attracted significant interests among researchers and developers because of its potentials for realizing spectrally-efficient wireless services at low complexity and costs. However, in multiuser MTMR systems, multiuser detection (MUD) techniques become more challenging, owing to the increased number of independent transmitter-receiver links, especially with multiple antennas at both ends. This paper investigates the performance of adaptive beamforming schemes suitable for multiuser MTMR OFDM-SDMA systems where both mobile users and base stations employ multiple transmit antennas. Using performance criteria such as mean-squared error (MSE) and signal-to-interference-plus noise ratio (SINR), we evaluate the performance of MTMR maximum ratio combining (MTMR-MRC) and the MTMR minimum mean-squared error (MTMR-MMSE) systems. In both schemes, it is shown that the level of interference dominates the detection of users' signal causing high error floor at low SINR and imposing restrictions on the number of transmit antennas.