Two Novel Channel-Augmentation Schemes for MIMO Systems

Recently, Rankin, Taylor, and Martin (RTM) 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 the RTM paper, we propose in this paper two channel-augmentation schemes having the same low complexity as the RTM scheme. In the first, the transmitted symbols are both repeated and complex conjugated leading to the conjugate virtual antenna (CVA) scheme. In the second, 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. The novel RVA and CVA schemes are seen to be more robust to channel correlation than the RTM scheme.