The use of smart antennas technology permits increasing the data rate and the quality of transmission. Due to this reason, in last years the study of Multi-Input-Multi-Output (MIMO) channels has been given an increasing importance. Simultaneously, the Orthogonal Frequency Division Multiplexing (OFDM) has been proposed for several communications and broadcasting systems due to the easy implementation of the (de)modulator and equalizer. In this paper we present and analyze several techniques that combine OFDM and arrays of antennas at both the transmitter and receiver. It is considered that Channel State Information (CSI) is available at both sides of the system, and a joint beamforming structure is proposed for the design of the front-ends. Within the proposed techniques, MAXMIN is shown to have a good performance with a low computational load.