VISA MIMO OFDM transmit scheme for wireless communications

The use of multiple antennas at the transmitter and the receiver results in enormous capacity increase. It has been well known that a spectral efficiency near the Shannon bound can be achieved in multi-input multi-output (MIMO) systems. However, such capacity is attained with penalty of tremendous receiver complexity. Time domain VISA (virtual subcarrier assignment) method has been first proposed for OFDM (orthogonal frequency division multiplexing) signal by Hara et al. (2003, 2004). Principle of the VISA structure is to deliberately color OFDM signals by different virtual subcarrier positions in the spectrum to enable adaptive array of antennas (AAA) to accept OFDM signal selectively. Due to the promising results, we extend the VISA concept, in this paper, into the frequency domain processing for MIMO (multi-input multi-output) transmission. To illustrate the performance of the proposed scheme, simulation results will be presented for QAM modulations.