Two Novel Channel Augmentation Schemes for MIMO Systems

Recently, Rankin, Taylor, and Martin (RTM) (Rankin, 2006) have proposed a simple channel augmentation scheme for multiple input multiple output (MIMO) systems. They have shown that the virtual receive antennas created by repeating the same transmit symbols several times can improve the outage rate of slow MIMO fading channels, especially if the number of transmit antennas is smaller than the number of receive antennas. Inspired by (Rankin, 2006) we propose in this paper two novel channel augmentation schemes which have the same complexity as the RTM scheme. In the first scheme, the transmitted symbols are not only repeated but also complex conjugated leading to the conjugate virtual antenna (CVA) scheme. In the second scheme, the transmitted symbols are constrained to be real-valued leading to the real virtual antenna (RVA) scheme. We show that the RTM, CVA, and RVA schemes can achieve a higher outage rate than the baseline scheme without augmentation for both V-BLAST and D-BLAST. Thereby, the novel RVA and CVA schemes are more robust to channel correlations than the RTM scheme.