ABBA-VBLAST hybrid space-time code for MIMO wireless communications

Hybrid MIMO communication systems combine spatial multiplexing with diversity gain to achieve both high spectral efficiency and link reliability. We present a novel hybrid scheme that allows the use of any number of spatial multiplexing layers, plus one quasi-orthogonal layer (ABBA) of either 3 or 4 antennas. We transform the system equations in terms of linear dispersion codes, from which we derive a low-complexity, ordered, successive interference cancellation receiver based on sorted QR decomposition. Symbol detection is carried out in a unified manner, both for spatial and space-time coded symbols. We show that this novel scheme outperforms other recent proposals in terms of bit error rate, even those using CSI at the transmitter to precode. We also show our proposal has lower complexity, achieved by exploiting the structure of the linear dispersion matrices.