On the capacity of stacked orthogonal space-time architecture over MIMO channels

We study the stacked orthogonal space-time code for the richly scattered Rayleigh fading multiple-input multiple-output (MIMO) channel, from an information theoretic perspective. It is known that the only capacity-achieving orthogonal space-time code is the Alamouti scheme. We show that the portion of the capacity that the stacked orthogonal space-time architecture can achieve is dependent on the number of transmit and receive antennas. In the high signal-to-noise ratio regime, the stacked orthogonal space-time code can achieve the channel capacity when the number of transmit antennas is no less than two times the number of receive antennas. Numerical simulations verify our conclusions.