Multi-user detection for MIMO-OFDM system using joint adaptive Beamforming

Joint beamforming with receive combining is a simple method for exploiting the significant diversity provided by multiple-input multiple-output (MIMO) systems, and the use of orthogonal frequency division multiplexing (OFDM) enables low complexity implementation of this scheme over frequency selective MIMO channels. In this paper we analyze the combination of MIMO systems with OFDM using joint beamforming in the multi user case where the receiver and the transmitter are equipped with antennas arrays in the reception and emission respectively. Under the assumption that all users´ channel state information (CSI) is available at each of the users, we will investigate the performance of conventional multi-user detector in the context of an uplink MIMO- OFDM system. Furthermore, we discuss orthogonal joint beamforming design schemes with matched filter receiver. Joint design of transmit and receive beamvectors are addressed. From this perspective, a set of design criteria can be easily accommodated and efficiently solved even though closed form expressions may not be available. Results shows that these criteria remain available in multiuser case and have the same performance classification then single user case.